Recombinant vectors

ABSTRACT

This disclosure provides modified cytosine deaminases (CDs). The disclosure further relates to cells and vector expressing or comprising such modified CDs and methods of using such modified CDs in the treatment of disease and disorders.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/477,741, which is a continuation of U.S. patent application Ser. No.13/072,704, filed Mar. 26, 2011 (now U.S. Pat. No. 8,829,173), which isa continuation-in-part of International Application No. PCT/US09/58512,filed Sep. 26, 2009, which claims priority to U.S. ProvisionalApplication Ser. No. 61/100,666, filed Sep. 26, 2008, U.S. ProvisionalApplication Ser. No. 61/120,618, filed Dec. 8, 2008, U.S. ProvisionalApplication Ser. No. 61/186,823, filed Jun. 13, 2009, and U.S.Provisional Application Ser. No. 61/318,728, filed Mar. 29, 2010, thedisclosures of which are incorporated herein by reference.

TECHNICAL FIELD

This disclosure relates to replication competent retroviral vectors fortreating cell proliferative. The disclosure further relates to the useof such replication competent retroviral vectors for delivery andexpression of heterologous nucleic acids.

BACKGROUND

Effective methods of delivering genes and heterologous nucleic acids tocells and subjects has been a goal researchers for scientificdevelopment and for possible treatments of diseases and disorders.

SUMMARY

The disclosure provides a recombinant replication competent retrovirus(RCR) comprising: a retroviral GAG protein; a retroviral POL protein; aretroviral envelope; a retroviral polynucleotide comprisingLong-Terminal Repeat (LTR) sequences at the 3′ end of the retroviralpolynucleotide sequence, a promoter sequence at the 5′ end of theretroviral polynucleotide, said promoter being suitable for expressionin a mammalian cell, a gag nucleic acid domain, a pol nucleic aciddomain and an env nucleic acid domain; a cassette comprising an internalribosome entry site (IRES) operably linked to a heterologouspolynucleotide, wherein the cassette is positioned 5′ to the 3′ LTR and3′ to the env nucleic acid domain encoding the retroviral envelope; andcis-acting sequences necessary for reverse transcription, packaging andintegration in a target cell, wherein the RCR maintains higherreplication competency after 6 passages compared to a pACE vector (SEQID NO:21). In one embodiment, the retroviral polynucleotide sequence isderived from murine leukemia virus (MLV), Moloney murine leukemia virus(MoMLV), Feline leukemia virus (FeLV) or Gibbon ape leukemia virus(GALV). In another embodiment, the MLV is an amphotropic MLV. In yetanother embodiment, the retrovirus is an oncoretrovirus or gammaretrovirus. In yet another embodiment, the target cell is a cell havinga cell proliferative disorder. The cell proliferative disorder can beselected from the group consisting of, but is not limited to, lungcancer, colon-rectum cancer, breast cancer, prostate cancer, urinarytract cancer, uterine cancer, brain cancer, head and neck cancer,pancreatic cancer, melanoma, stomach cancer and ovarian cancer,rheumatoid arthritis and other autoimmune diseases. In one embodiment,the promoter comprises a CMV promoter having a sequence as set forth inSEQ ID NO:19, 20 or 22 from nucleotide 1 to about nucleotide 582 and mayinclude modification to one or more nucleic acid bases and which iscapable of directing and initiating transcription. In yet a furtherembodiment, the promoter comprises a sequence as set forth in SEQ ID NO:19, 20 or 22 from nucleotide 1 to about nucleotide 582. In a furtherembodiment, the promoter comprises a CMV-R-U5 domain polynucleotide. Inone embodiment, the CMV-R-U5 domain comprises the immediately earlypromoter from human cytomegalovirus linked to an MLV R-U5 region. In yetanother embodiment, the CMV-R-U5 domain polynucleotide comprises asequence as set forth in SEQ ID NO: 19, 20 or 22 from about nucleotide 1to about nucleotide 1202 or sequences that are at least 95% identical toa sequence as set forth in SEQ ID NO: 19, 20 or 22, wherein thepolynucleotide promotes transcription of a nucleic acid moleculeoperably linked thereto. In another embodiment, the gag and pol of thepolynucleotide are derived from an oncoretrovirus or gamma retrovirus.The gag nucleic acid domain can comprise a sequence from aboutnucleotide number 1203 to about nucleotide 2819 of SEQ ID NO: 19 or 22or a sequence having at least 95%, 98%, 99% or 99.8% identity thereto.The pol domain can comprise a sequence from about nucleotide number 2820to about nucleotide 6358 of SEQ ID NO: 19 or 22 or a sequence having atleast 95%, 98%, 99% or 99.9% identity thereto. In one embodiment, theenv domain encodes an amphotropic env protein. The env domain cancomprise a sequence from about nucleotide number 6359 to aboutnucleotide 8323 of SEQ ID NO: 19 or 22 or a sequence having at least95%, 98%, 99% or 99.8% identity thereto. The IRES domain of the vectorcan be any IRES, however, in one embodiment the IRES is derived from anencephalomyocarditis virus. In a further embodiment, the IRES comprisesa sequence from about nucleotide number 8327 to about nucleotide 8876 ofSEQ ID NO: 19 or 22 or a sequence having at least 95%, 98%, or 99%identity thereto.

The vector can comprise any number of different heterologouspolynucleotides. For example, the heterologous polynucleotide cancomprise a cytokine, an siRNA, miRNA or RNAi molecules, a targetingsequence, a binding domain, a cytotoxic gene, a single chain antibody orany combination thereof. When the heterologous polynucleotide is for anon-translated RNA such as siRNA, miRNA or RNAi then no IRES isnecessary, but may be included for another translated gene RNA, and anykind of retrovirus can be used. In yet a further embodiment, theheterologous polynucleotide comprises a polynucleotide having a sequenceas set forth in SEQ ID NO: 3, 5, 11, 13, 15 or 17. In a furtherembodiment, the heterologous sequence encodes a polypeptide comprising asequence as set forth in SEQ ID NO: 4. The heterologous nucleic acid ishuman codon optimized and encodes a polypeptide as set forth in SEQ IDNO:4. In a further embodiment, the heterologous nucleic acid comprises asequence as set forth in SEQ ID NO: 19 or 22 from about nucleotidenumber 8877 to about 9353. In one embodiment, the 3′ LTR is derived froman oncoretrovirus or gamma-retrovirus. In a further embodiment, the 3′LTR comprises a U3-R-U5 domain. In yet a further embodiment, the 3′ LTRcomprises a sequence as set forth in SEQ ID NO: 19 from about nucleotide9405 to about 9998 or a sequence that is at least 95%, 98% or 99.5%identical thereto.

The disclosure provides a polynucleotide comprising a sequence as setforth in SEQ ID NO: 19, 20 or 22.

The disclosure provides an isolated polynucleotide comprising from 5′ to3′: a CMV-R-U5 fusion of the immediate early promoter from humancytomegalovirus to an MLV R-U5 region; a PBS, primer binding site forreverse transcriptase; a 5′ splice site; ψ packaging signal; a gagcoding sequence for MLV group specific antigen; a pol coding sequencefor MLV polymerase polyprotein; a 3′ splice site; a 4070A env codingsequence for envelope protein of MLV strain 4070A; an internal ribosomeentry site (IRES) from encephalomyocarditis virus; a modified cytosinedeaminase coding sequence; a polypurine tract; and a U3-R-U5 MLV longterminal repeat.

The disclosure provides a method of treating a subject with a cellproliferative disorder comprising contacting the subject with apolynucleotide encoding a polypeptide of the disclosure having cytosinedeaminase activity under conditions such that the polynucleotide isexpressed, and contacting the subject with 5-fluorocytosine.

The disclosure also provides a method of treating a cell proliferativedisorder in a subject comprising contacting the subject with aretrovirus of the disclosure, wherein the heterologous nucleic acidsequence encodes a therapeutic protein that inhibits proliferation of aneoplastic cell. In one embodiment, the retrovirus comprises apolynucleotide encoding a polypeptide having a sequence as set forth inSEQ ID NO: 4, 12, 14, 16, or 18.

The disclosure provides a recombinant replication competent retrovirus(RCR) comprising recombinant replication competent retrovirus, whereinthe vector infects the target multiple times leading to a mean of 5 ormore copies of the retrovirus genome. The multiple copies provide a“super” infection useful for gene delivery and protein production invivo and in vitro. In one embodiment, the recombinant replicationcompetent retrovirus (RCR) comprises: a retroviral GAG protein; aretroviral POL protein; a retroviral envelope; a retroviralpolynucleotide comprising Long-Terminal Repeat (LTR) sequences at the 3′end of the retroviral polynucleotide sequence, a promoter sequence atthe 5′ end of the retroviral polynucleotide, said promoter beingsuitable for expression in a mammalian cell, a gag nucleic acid domain,a pol nucleic acid domain and an env nucleic acid domain; a cassettecomprising an internal ribosome entry site (IRES) operably linked to aheterologous polynucleotide, wherein the cassette is positioned 5′ tothe 3′ LTR and 3′ to the env nucleic acid domain encoding the retroviralenvelope; and cis-acting sequences necessary for reverse transcription,packaging and integration in a target cell, wherein the RCR maintainshigher replication competency after 6 passages compared to a pACE vector(SEQ ID NO:21). In one embodiment, the retroviral polynucleotidesequence is derived from murine leukemia virus (MLV), Moloney murineleukemia virus (MoMLV), Feline leukemia virus (FeLV), Baboon endogenousretrovirus (BEV), porcine endogenous virus (PERV), the cat derivedretrovirus RD114, squirrel monkey retrovirus, Xenotropic murine leukemiavirus-related virus (XMRV), avian reticuloendotheliosis virus (REV), orGibbon ape leukemia virus (GALV). In another embodiment, the MLV is anamphotropic MLV. In yet another embodiment, the retrovirus is anoncoretrovirus or gamma retrovirus. In yet another embodiment, thetarget cell is a cell having a cell proliferative disorder. The cellproliferative disorder can be selected from the group consisting of, butis not limited to, lung cancer, colon-rectum cancer, breast cancer,prostate cancer, urinary tract cancer, uterine cancer, brain cancer,head and neck cancer, pancreatic cancer, melanoma, stomach cancer andovarian cancer, rheumatoid arthritis and other autoimmune diseases. Inone embodiment, the promoter comprises a CMV promoter having a sequenceas set forth in SEQ ID NO:19, 20 or 22 from nucleotide 1 to aboutnucleotide 582 and may include modification to one or more nucleic acidbases and which is capable of directing and initiating transcription. Inyet a further embodiment, the promoter comprises a sequence as set forthin SEQ ID NO: 19, 20 or 22 from nucleotide 1 to about nucleotide 582. Ina further embodiment, the promoter comprises a CMV-R-U5 domainpolynucleotide. In one embodiment, the CMV-R-U5 domain comprise theimmediately early promoter from human cytomegalovirus linked to an MLVR-U5 region. In yet another embodiment, the CMV-R-U5 domainpolynucleotide comprises a sequence as set forth in SEQ ID NO: 19, 20 or22 from about nucleotide 1 to about nucleotide 1202 or sequences thatare at least 95% identical to a sequence as set forth in SEQ ID NO: 19,20 or 22, wherein the polynucleotide promotes transcription of a nucleicacid molecule operably linked thereto. In another embodiment, the gagand pol of the polynucleotide are derived from an oncoretrovirus orgamma retrovirus. The gag nucleic acid domain can comprise a sequencefrom about nucleotide number 1203 to about nucleotide 2819 of SEQ ID NO:19 or 22 or a sequence having at least 95%, 98%, 99% or 99.8% identitythereto. The pol domain can comprise a sequence from about nucleotidenumber 2820 to about nucleotide 6358 of SEQ ID NO: 19 or 22 or asequence having at least 95%, 98%, 99% or 99.9% identity thereto. In oneembodiment, the env domain encodes an amphotropic env protein. The envdomain can comprise a sequence from about nucleotide number 6359 toabout nucleotide 8323 of SEQ ID NO: 19 or 22 or a sequence having atleast 95%, 98%, 99% or 99.8% identity thereto. The IRES domain of thevector can be any IRES, however, in one embodiment the IRES is derivedfrom an encephalomyocarditis virus. In a further embodiment, the IREScomprises a sequence from about nucleotide number 8327 to aboutnucleotide 8876 of SEQ ID NO: 19 or 22 or a sequence having at least95%, 98%, or 99% identity thereto.

The disclosure provides a method of treating a cell proliferativedisorder in a subject comprising contacting the subject with aretrovirus of the disclosure wherein the vector infects the targetmultiple times leading to a mean of 5 or more copies of the retrovirusgenome.

The details of one or more embodiments of the disclosure are set forthin the accompanying drawings and the description below. Other features,objects, and advantages will be apparent from the description anddrawings, and from the claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A-C shows an alignment of the Wild-type yeast cytosine deaminase(SEQ ID NO: 2) and a cytosine deaminase of the disclosure (SEQ ID NO: 4)and other sequences of the disclosure (SEQ ID NOs:31-40).

FIG. 2 shows a graph of cell killing data showing that modified vectorsare more effective compared to the original wild type CD. The graph alsoshows that the new modified backbone (T5.0007) is more effective atkilling than the old backbone (pACE-CD). Also shown is a tablecataloguing the various vector constructs and their names.

FIG. 3A-F shows (A) a schematic of a recombinant retroviral vector ofthe disclosure; (B-C) a plasmid map of a polynucleotide of thedisclosure; (D) a sequence of a polynucleotide of the disclosure (SEQ IDNO:19); the vector coding region of pAC3-yCD2 in various formats (i.e.,FIG. 3D-1 to 3D-2 shows the domains of the vector and FIG. 3D-4 to FIG.3D-16 shows restriction sites in the vector of SEQ ID NO:19); (E)Diagram of changes between pACE-emdGFP and pAC3-emdGFP; (F) showsadditional plasmid map details of SEQ ID NO:19 (FIG. 3F-1 and FIG. 3F-2)and FIG. 3F-3 to FIG. 3F-5) shows the sequence of SEQ ID NO:22 includingidentifying various domains; and (FIG. 3F-6 to FIG. 3F-18) showsrestriction sites in the vector of SEQ ID NO:22.

FIG. 4 shows that higher levels of yCD2 protein are observed compared towild type yCD protein in infected U-87 cells.

FIG. 5 shows that a vector of the disclosure is genetically stable after12 cycles of viral passages as assessed using PCR amplification. Thefigure also demonstrates that the vectors of the disclosure are morestable after longer passages compared to the vector pACE-CD (Kasahara etal.). In particular pAC3-CD is more stable than pACE-CD, demonstratingthat the changed backbone has made the vector more stable. In additionpACE-yCD1 (T5.0001) and -yCD2 (T5-0002) are very much more stable thanpAC-yCD, demonstrating that small and silent changes to the codingsequence of the transgene can have a very large effect on stability,leading to superior properties.

FIG. 6A-B shows (A) cell killing assays; and (B) cytosine deaminasespecific activity of cells infected with different vectors. (A) showsthat cytosine deaminase and vector of the disclosure kill infected cellsat least as well and perhaps better than the original pACE-CD when U87infected cells are exposed to increasing levels of 5-FC. (B) Shows thatthe specific CD activity of the disclosure (T5.0007, T5.0001 andT5.0002) are all increased compared to pACE-CD (T5.0000), and is in theorder T5.0000<T5.0007<T5.0001<T5.0002.

FIG. 7 shows U-87 tumors treated with CD vector of the disclosure invivo and explanted from mice treated with 4 cycles of 5-FC are stillsensitive to the drug.

FIG. 8 shows dosing information and therapeutic effect in a Kaplan-Meyersurvival analysis in a mouse model of brain cancer.

FIG. 9 shows dosing information and therapeutic effect in a Kaplan-Meyersurvival analysis in a syngeneic mouse model.

FIG. 10A-D shows schemes for the generation of various embodiments ofthe disclosure comprising polypeptide with CD, OPRT and UPRT activity.

FIG. 11A-E shows vector maps and miRNA results. A. is a schematic vectormap of the MLV retroviral vector pAC3 backbone containing polynucleotidesequences of human primary precursor miR-128-1, human primary precursormiR-128-2 and human precursor miR-128 linked to a human H1 promoter,designated pAC3-miR128-1, pAC3-miR-128-2, and pAC3-H1-shRNAmiR128,respectively. B. is a schematic vector map of the MLV retroviral vectorpAC3-yCD2 backbone containing polynucleotide sequences of a humanprecursor miR-128 linked to a human H1 promoter, designatedpAC3-yCD2-H1-shRNAmiR128. C. shows a schematic vector map of the MLVretroviral vector pAC3 backbone containing polynucleotide sequences ofhuman primary precursor miR-142-3pT. D. shows sequences for 142-3p (SEQID NOs: 35 and 36) and primers (SEQ ID NO:41 and 42). E. shows resultsfrom transformation with a vector containing miR-142-3pT.

FIG. 12A-B: A. shows a comparison of replication kinetics of miR-128containing vectors (pAC3-miR-128-1, pAC3-miR-128-2, andpAC3-H1-shRNAmiR128) in human fibrosarcoma cells HT1080 analyzed byqPCR. The graph is generated by plotting of inversed C(t) valuesobtained from qPCR vs. various time points during viral replication. B.shows a comparison of replication kinetics of miR-128 containing vectors(pAC3-miR-128-1, pAC3-miR-128-2, and pAC3-H1-shRNAmiR128) in humanglioma cells U87-MG analyzed by qPCR. The graph is generated by plottingof inversed C(t) values obtained from qPCR vs. various time pointsduring viral replication.

FIG. 13 shows a relative quantification of mature miR-128 expressionfrom cells transduced with miR-128 containing vectors.

FIG. 14 shows a relative quantification of Bmi-1 gene expression fromcells transduced with miR-128 containing vectors.

FIG. 15 is a schematic vector map of the MLV retroviral vector pAC3-emdcontaining a single copy of 142-3pT target sequence, designatedpAC3-emd-142-3pT and 4 tandem repeats of 142-3pT, designatedpAC3-emd-142-3pT4X.

FIG. 16 is a schematic vector map of the MLV retroviral vector pAC3-yCD2containing a single copy of 142-3pT target sequence, designatedpAC3-yCD2-142-3pT and 4 tandem repeats of 142-3pT, designatedpAC3-yCD2-142-3pT4X.

FIG. 17A-B: A. shows a comparison of replication kinetics of 142-3pTcontaining vectors (pAC3-emd-142-3pT pAC3-emd-142-3pT4X,pAC3-yCD2-142-3pT and pAC3-yCD2-142-3pT4X) and their parental vectors(pAC3-emd and pAC3-yCD2) in human fibrosarcoma cells HT1080 analyzedqPCR. The graph is generated by plotting by inversed C(t) valuesobtained from qPCR vs. various time points during viral replication. B.shows a comparison of replication kinetics of GFP containing vectors(pAC3-emd, pAC3-emd-142-3pT and pAC3-emd-142-3pT4X) in humanfibrosarcoma cells HT1080 analyzed by flow cytometric analysis of GFPexpression at various time points during vector spread.

FIG. 18A-B: A. shows a comparison of replication kinetics of 142-3pTcontaining vectors (pAC3-emd-142-3pT pAC3-emd-142-3pT4X,pAC3-yCD2-142-3pT and pAC3-yCD2-142-3pT4X) and their parental vectors(pAC3-emd and pAC3-yCD2) in human glioma cells U87-MG analyzed qPCR. Thegraph is generated by plotting by inversed C(t) values obtained fromqPCR vs. various time points during viral replication. B. shows acomparison of replication kinetics of GFP containing vectors (pAC3-emd,pAC3-emd-142-3pT and pAC3-emd-142-3pT4X) in human glioma cells U87-MGanalyzed by flow cytometric analysis of GFP expression at various timepoints during vector spread.

FIG. 19 shows the replication kinetics of GFP containing vector(pAC3-emd) in mouse and human hematopoietic cells analyzed by flowcytometric analysis of GFP expression at various time points duringvector spread.

FIG. 20A-C shows comparison of replication kinetics. A. shows acomparison of replication kinetics of GFP containing vectors (pAC3-emd,pAC3-emd-142-3pT and pAC3-emd-142-3pT4X) in mouse T-lymphocytes EL4analyzed by flow cytometric analysis of GFP expression at various timepoints during vector spread. B. shows a comparison of replicationkinetics of GFP containing vectors (pAC3-emd, pAC3-emd-142-3pT andpAC3-emd-142-3pT4X) in human T-lymphocytes SUP-T1 analyzed by flowcytometric analysis of GFP expression at various time points duringvector spread. C. shows a comparison of replication kinetics of GFPcontaining vectors (pAC3-emd, pAC3-emd-142-3pT and pAC3-emd-142-3pT4X)in human monocytes U937 analyzed by flow cytometric analysis of GFPexpression at various time points during vector spread.

FIGS. 21A-B are still frames from the MRI images obtained from thepatient dog during intratumoral CED infusion of Toca 511 and gadolinium.Note the large tumor on the left side of the image compressing bothsides of the brain and shifting midline structures to the right. Thewhite areas are the gadolinium-Toca 511 infusion. FIG. 21B shows theplacement of the two catheters into the tumor.

FIG. 22 is a schematic vector map of the MLV retroviral vectors encodingthe human IFN-gamma (hIFNg) and mouse IFN-gamma (mIFNg), respectively,in pAC3 backbone.

FIG. 23 shows the expression of mIFN-gamma at the RNA level from humanfibrosarcoma cell line HT1080 infected with pAC3-mIFNg vector.Expression is detected by RT-PCR.

FIG. 24 shows the expression of hIFN-gamma protein secreted from humanfibrosarcoma cell line HT1080 infected with pAC3-hIFNg vector.

FIG. 25 shows the expression of mIFN-gamma protein secreted from humanfibrosarcoma cell line HT1080 infected with pAC3-mIFNg vector.

FIG. 26 shows flow cytometry analysis of GFP expression in U87 cellsafter intratumor or intravenous delivery of AC3-GFP vector in a nudemouse model. Cells are measured by flow cytometry for percent GFPpositive. Cells isolated from naïve nude mouse brains, U87 cells fromtissue culture, or U87 cells transduced at an multiplicity of infectionof 1 with AC3-GFP(V) in vitro serve as controls. From example 27 (ivinjection of GFP vector).

FIG. 27 shows a histogram analysis was also done on groups 1, 3 and 5from example 27 (iv injection of GFP vector) to measure the distributionof GFP signal in isolated U87 cells. GFP expression is from U87 tumorcells isolated from mouse brains after 14 days after vector treatment.

FIG. 28 is a schematic vector map of the MLV retroviral vectors encodingthe human IL-2 in the pAC3 backbone.

DETAILED DESCRIPTION

As used herein and in the appended claims, the singular forms “a,”“and,” and “the” include plural referents unless the context clearlydictates otherwise. Thus, for example, reference to “a cell” includes aplurality of such cells and reference to “the agent” includes referenceto one or more agents known to those skilled in the art, and so forth.

Also, the use of “or” means “and/or” unless stated otherwise. Similarly,“comprise,” “comprises,” “comprising” “include,” “includes,” and“including” are interchangeable and not intended to be limiting.

It is to be further understood that where descriptions of variousembodiments use the term “comprising,” those skilled in the art wouldunderstand that in some specific instances, an embodiment can bealternatively described using language “consisting essentially of” or“consisting of.”

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood to one of ordinary skill inthe art to which this disclosure belongs. Although methods and materialssimilar or equivalent to those described herein can be used in thepractice of the disclosed methods and compositions, the exemplarymethods, devices and materials are described herein.

General texts which describe molecular biological techniques usefulherein, including the use of vectors, promoters and many other relevanttopics, include Berger and Kimmel, Guide to Molecular CloningTechniques, Methods in Enzymology Volume 152, (Academic Press, Inc., SanDiego, Calif.) (“Berger”); Sambrook et al., Molecular Cloning—ALaboratory Manual, 2d ed., Vol. 1-3, Cold Spring Harbor Laboratory, ColdSpring Harbor, N.Y., 1989 (“Sambrook”) and Current Protocols inMolecular Biology, F. M. Ausubel et al., eds., Current Protocols, ajoint venture between Greene Publishing Associates, Inc. and John Wiley& Sons, Inc., (supplemented through 1999) (“Ausubel”). Examples ofprotocols sufficient to direct persons of skill through in vitroamplification methods, including the polymerase chain reaction (PCR),the ligase chain reaction (LCR), Qβ-replicase amplification and otherRNA polymerase mediated techniques (e.g., NASBA), e.g., for theproduction of the homologous nucleic acids of the disclosure are foundin Berger, Sambrook, and Ausubel, as well as in Mullis et al. (1987)U.S. Pat. No. 4,683,202; Innis et al., eds. (1990) PCR Protocols: AGuide to Methods and Applications (Academic Press Inc. San Diego,Calif.) (“Innis”); Arnheim & Levinson (Oct. 1, 1990) C&EN 36-47; TheJournal Of NIH Research (1991) 3: 81-94; Kwoh et al. (1989) Proc. Natl.Acad. Sci. USA 86: 1173; Guatelli et al. (1990) Proc. Nat'l. Acad. Sci.USA 87: 1874; Lomell et al. (1989) J. Clin. Chem 35: 1826; Landegren etal. (1988) Science 241: 1077-1080; Van Brunt (1990) Biotechnology 8:291-294; Wu and Wallace (1989) Gene 4:560; Barringer et al. (1990) Gene89:117; and Sooknanan and Malek (1995) Biotechnology 13: 563-564.Improved methods for cloning in vitro amplified nucleic acids aredescribed in Wallace et al., U.S. Pat. No. 5,426,039. Improved methodsfor amplifying large nucleic acids by PCR are summarized in Cheng et al.(1994) Nature 369: 684-685 and the references cited therein, in whichPCR amplicons of up to 40 kb are generated. One of skill will appreciatethat essentially any RNA can be converted into a double stranded DNAsuitable for restriction digestion, PCR expansion and sequencing usingreverse transcriptase and a polymerase. See, e.g., Ausubel, Sambrook andBerger, all supra.

The publications discussed throughout the text are provided solely fortheir disclosure prior to the filing date of the present application.Nothing herein is to be construed as an admission that the inventors arenot entitled to antedate such disclosure by virtue of prior disclosure.

The disclosure provides methods and compositions useful for gene orprotein delivery to a cell or subject. Such methods and compositions canbe used to treat various diseases and disorders in a subject includingcancer and other cell proliferative diseases and disorders. Thedisclosure provides replication competent retroviral vectors for genedelivery.

The terms “vector”, “vector construct” and “expression vector” mean thevehicle by which a DNA or RNA sequence (e.g. a foreign gene) can beintroduced into a host cell, so as to transform the host and promoteexpression (e.g. transcription and translation) of the introducedsequence. Vectors typically comprise the DNA of a transmissible agent,into which foreign DNA encoding a protein is inserted by restrictionenzyme technology. A common type of vector is a “plasmid”, whichgenerally is a self-contained molecule of double-stranded DNA that canreadily accept additional (foreign) DNA and which can readily introducedinto a suitable host cell. A large number of vectors, including plasmidand fungal vectors, have been described for replication and/orexpression in a variety of eukaryotic and prokaryotic hosts.Non-limiting examples include pKK plasmids (Clonetech), pUC plasmids,pET plasmids (Novagen, Inc., Madison, Wis.), pRSET or pREP plasmids(Invitrogen, San Diego, Calif.), or pMAL plasmids (New England Biolabs,Beverly, Mass.), and many appropriate host cells, using methodsdisclosed or cited herein or otherwise known to those skilled in therelevant art. Recombinant cloning vectors will often include one or morereplication systems for cloning or expression, one or more markers forselection in the host, e.g., antibiotic resistance, and one or moreexpression cassettes.

The terms “express” and “expression” mean allowing or causing theinformation in a gene or DNA sequence to become manifest, for exampleproducing a protein by activating the cellular functions involved intranscription and translation of a corresponding gene or DNA sequence. ADNA sequence is expressed in or by a cell to form an “expressionproduct” such as a protein. The expression product itself, e.g. theresulting protein, may also be said to be “expressed” by the cell. Apolynucleotide or polypeptide is expressed recombinantly, for example,when it is expressed or produced in a foreign host cell under thecontrol of a foreign or native promoter, or in a native host cell underthe control of a foreign promoter.

The disclosure provides replication competent viral vectors the containa heterologous polynucleotide encoding, for example, a cytosinedeaminase or mutant thereof, an miRNA or siRNA, a cytokine, an antibodybinding domain etc., that can be delivered to a cell or subject. Theviral vector can be an adenoviral vector, a measles vector, a herpesvector, a retroviral vector (including a lentiviral vector), arhabdoviral vector such as a Vesicular Stomatitis viral vector, areovirus vector, a Seneca Valley Virus vector, a poxvirus vector(including animal pox or vaccinia derived vectors), a parvovirus vector(including an AAV vector), an alphavirus vector or other viral vectorknown to one skilled in the art (see also, e.g., Concepts in GeneticMedicine, ed. Boro Dropulic and Barrie Carter, Wiley, 2008, Hoboken,N.J.; The Development of Human Gene Therapy, ed. Theodore Friedmann,Cold Springs Harbor Laboratory Press, Cold springs Harbor, N.Y., 1999;Gene and Cell Therapy, ed. Nancy Smyth Templeton, Marcel Dekker Inc.,New York, N.Y., 2000 and Gene Therapy: Therapeutic Mechanism andStrategies, ed. Nancy Smyth Templetone and Danilo D Lasic, MarcelDekker, Inc., New York, N.Y., 2000; the disclosures of which areincorporated herein by reference).

In one embodiment, the viral vector can be a replication competentretroviral vector capable of infecting only replicating mammalian cells.In one embodiment, a replication competent retroviral vector comprisesan internal ribosomal entry site (IRES) 5′ to the heterologouspolynucleotide encoding, e.g., a cytosine deaminase, miRNA, siRNA,cytokine, receptor, antibody or the like. When the heterologouspolynucleotide encodes a non-translated RNA such as siRNA, miRNA or RNAithen no IRES is necessary, but may be included for another translatedgene, and any kind of retrovirus (see below) can be used. In oneembodiment, the polynucleotide is 3′ to a ENV polynucleotide of aretroviral vector. In one embodiment the viral vector is a retroviralvector capable of infecting target cells multiple times (5 or more perdiploid cell).

In other embodiments, host cells transfected with a replicationcompetent retroviral vector of the disclosure are provided. Host cellsinclude eukaryotic cells such as yeast cells, insect cells, or animalcells. Host cells also include prokaryotic cells such as bacterialcells.

Also provided are engineered host cells that are transduced (transformedor transfected) with a vector provided herein (e.g., a replicationcompetent retroviral vector). The engineered host cells can be culturedin conventional nutrient media modified as appropriate for activatingpromoters, selecting transformants, or amplifying a codingpolynucleotide. Culture conditions, such as temperature, pH and thelike, are those previously used with the host cell selected forexpression, and will be apparent to those skilled in the art and in thereferences cited herein, including, e.g., Sambrook, Ausubel and Berger,as well as e.g., Freshney (1994) Culture of Animal Cells: A Manual ofBasic Technique, 3rd ed. (Wiley-Liss, New York) and the references citedtherein.

Examples of appropriate expression hosts include: bacterial cells, suchas E. coli, B. subtilis, Streptomyces, and Salmonella typhimurium;fungal cells, such as Saccharomyces cerevisiae, Pichia pastoris, andNeurospora crassa; insect cells such as Drosophila and Spodopterafrugiperda; mammalian cells such as CHO, COS, BHK, HEK 293 br Bowesmelanoma; or plant cells or explants, etc. Typically human cells or celllines will be used; however, it may be desirable to clone vectors andpolynucleotides of the disclosure into non-human host cells for purposesof sequencing, amplification and cloning.

The disclosure also provides replication competent retroviral vectorshaving increased stability relative to prior retroviral vectors. Suchincreased stability during infection and replication is important forthe treatment of cell proliferative disorders. The combination oftransduction efficiency, transgene stability and target selectivity isprovided by the replication competent retrovirus. The compositions andmethods provide insert stability and maintain transcription activity ofthe transgene and the translational viability of the encodedpolypeptide.

The disclosure provides modified retroviral vectors. The modifiedretroviral vectors can be derived from members of the retroviridaefamily. The Retroviridae family consists of three groups: thespumaviruses-(or foamy viruses) such as the human foamy virus (HFV); thelentiviruses, as well as visna virus of sheep; and the oncoviruses(although not all viruses within this group are oncogenic). The term“lentivirus” is used in its conventional sense to describe a genus ofviruses containing reverse transcriptase. The lentiviruses include the“immunodeficiency viruses” which include human immunodeficiency virus(HIV) type 1 and type 2 (HIV-1 and HIV-2) and simian immunodeficiencyvirus (SIV). The oncoviruses have historically been further subdividedinto groups A, B, C and D on the basis of particle morphology, as seenunder the electron microscope during viral maturation. A-type particlesrepresent the immature particles of the B- and D-type viruses seen inthe cytoplasm of infected cells. These particles are not infectious.B-type particles bud as mature virion from the plasma membrane by theenveloping of intracytoplasmic A-type particles. At the membrane theypossess a toroidal core of 75 nm, from which long glycoprotein spikesproject. After budding, B-type particles contain an eccentricallylocated, electron-dense core. The prototype B-type virus is mousemammary tumor virus (MMTV). No intracytoplasmic particles can beobserved in cells infected by C-type viruses. Instead, mature particlesbud directly from the cell surface via a crescent ‘C’-shapedcondensation which then closes on itself and is enclosed by the plasmamembrane. Envelope glycoprotein spikes may be visible, along with auniformly electron-dense core. Budding may occur from the surface plasmamembrane or directly into intracellular vacuoles. The C-type viruses arethe most commonly studied and include many of the avian and murineleukemia viruses (MLV). Bovine leukemia virus (BLV), and the humanT-cell leukemia viruses types I and II (HTLV-I/II) are similarlyclassified as C-type particles because of the morphology of theirbudding from the cell surface. However, they also have a regularhexagonal morphology and more complex genome structures than theprototypic C-type viruses such as the murine leukemia viruses (MLV).D-type particles resemble B-type particles in that they show asring-like structures in the infected cell cytoplasm, which bud from thecell surface, but the virion incorporate short surface glycoproteinspikes. The electron-dense cores are also eccentrically located withinthe particles. Mason Pfizer monkey virus (MPMV) is the prototype D-typevirus.

Retroviruses have been classified in various ways but the nomenclaturehas been standardized in the last decade (see ICTVdB—The Universal VirusDatabase, v 4 on the World Wide Web (www) atncbi.nlm.nih.gov/ICTVdb/ICTVdB/ and the text book “Retroviruses” EdsCoffin, Hughs and Varmus, Cold Spring Harbor Press 1997; the disclosuresof which are incorporated herein by reference). In one embodiment, thereplication competent retroviral vector can comprise an Orthoretrovirusor more typically a gamma retrovirus vector.

Retroviruses are defined by the way in which they replicate theirgenetic material. During replication the RNA is converted into DNA.Following infection of the cell a double-stranded molecule of DNA isgenerated from the two molecules of RNA which are carried in the viralparticle by the molecular process known as reverse transcription. TheDNA form becomes covalently integrated in the host cell genome as aprovirus, from which viral RNAs are expressed with the aid of cellularand/or viral factors. The expressed viral RNAs are packaged intoparticles and released as infectious virion.

The retrovirus particle is composed of two identical RNA molecules. Eachwild-type genome has a positive sense, single-stranded RNA molecule,which is capped at the 5′ end and polyadenylated at the 3′ tail. Thediploid virus particle contains the two RNA strands complexed with gagproteins, viral enzymes (pol gene products) and host tRNA moleculeswithin a ‘core’ structure of gag proteins. Surrounding and protectingthis capsid is a lipid bilayer, derived from host cell membranes andcontaining viral envelope (env) proteins. The env proteins bind to acellular receptor for the virus and the particle typically enters thehost cell via receptor-mediated endocytosis and/or membrane fusion.

After the outer envelope is shed, the viral RNA is copied into DNA byreverse transcription. This is catalyzed by the reverse transcriptaseenzyme encoded by the pol region and uses the host cell tRNA packagedinto the virion as a primer for DNA synthesis. In this way the RNAgenome is converted into the more complex DNA genome.

The double-stranded linear DNA produced by reverse transcription may, ormay not, have to be circularized in the nucleus. The provirus now hastwo identical repeats at either end, known as the long terminal repeats(LTR). The termini of the two LTR sequences produces the site recognizedby a pol product—the integrase protein—which catalyzes integration, suchthat the provirus is always joined to host DNA two base pairs (bp) fromthe ends of the LTRs. A duplication of cellular sequences is seen at theends of both LTRs, reminiscent of the integration pattern oftransposable genetic elements. Retroviruses can integrate their DNAs atmany sites in host DNA, but different retroviruses have differentintegration site preferences. HIV-1 and simian immunodeficiency virusDNAs preferentially integrate into expressed genes, murine leukemiavirus (MLV) DNA preferentially integrates near transcriptional startsites (TSSs), and avian sarcoma leukosis virus (ASLV) and human T cellleukemia virus (HTLV) DNAs integrate nearly randomly, showing a slightpreference for genes (Derse D, et al. (2007) Human T-cell leukemia virustype 1 integration target sites in the human genome: comparison withthose of other retroviruses. J Virol 81:6731-6741; Lewinski M K, et al.(2006) Retroviral DNA integration: viral and cellular determinants oftarget-site selection. PLoS Pathog 2:e601).

Transcription, RNA splicing and translation of the integrated viral DNAis mediated by host cell proteins. Variously spliced transcripts aregenerated. In the case of the human retroviruses HIV-1/2 and HTLV-I/IIviral proteins are also used to regulate gene expression. The interplaybetween cellular and viral factors is a factor in the control of viruslatency and the temporal sequence in which viral genes are expressed.

Retroviruses can be transmitted horizontally and vertically. Efficientinfectious transmission of retroviruses requires the expression on thetarget cell of receptors which specifically recognize the viral envelopeproteins, although viruses may use receptor-independent, nonspecificroutes of entry at low efficiency. Normally a viral infection leads to asingle or few copies of viral genome per cell because of receptormasking or down-regulation that in turn leads to resistance tosuperinfection (Ch3 p104 in “Retroviruses” J M Coffin, S H Hughes, & H EVarmus 1997 Cold Spring Harbor Laboratory Press, Cold Spring HarborN.Y.; Fan et al. J. Virol 28:802, 1978). By manipulating the situationin tissue culture it is possible to get some level of multiple infectionbut this is less than 5 copies/diploid genome. In addition, the targetcell type must be able to support all stages of the replication cycleafter virus has bound and penetrated. Vertical transmission occurs whenthe viral genome becomes integrated in the germ line of the host. Theprovirus will then be passed from generation to generation as though itwere a cellular gene. Hence endogenous proviruses become establishedwhich frequently lie latent, but which can become activated when thehost is exposed to appropriate agents.

In many situations for using a recombinant replication competentretrovirus therapeutically, it is advantageous to have high levels ofexpression of the transgene that is encoded by the recombinantreplication competent retrovirus. For example, with a prodrug activatinggene such as the cytosine deaminase gene it is advantageous to havehigher levels of expression of the CD protein in a cell so that theconversion of the prodrug 5-FC to 5-FU is more efficient. Similarly highlevels of expression of siRNA or shRNA lead to more efficientsuppression of target gene expression. Also for cytokines or singlechain antibodies (scAbs) it is usually advantageous to express highlevels of the cytokine or scAb. In addition, in the case that there aremutations in some copies of the vector that inactivate or impair theactivity of the vector or transgene, it is advantageous to have multiplecopies of the vector in the target cell as this provides a highprobability of efficient expression of the intact transgene. Thedisclosure provides recombinant replication competent retrovirusescapable of infecting a target cell or target cell population multipletimes resulting in an average number of copies/diploid genome of 5 orgreater. The disclosure also provides methods of testing for thisproperty. Also provided are methods of treating a cell proliferativedisorder, using a recombinant replication competent retrovirus capableof infecting a target cell or target cell population multiple timesresulting in an average number of copies/diploid genome of 5 or greater.

As mentioned above, the integrated DNA intermediate is referred to as aprovirus. Prior gene therapy or gene delivery systems use methods andretroviruses that require transcription of the provirus and assemblyinto infectious virus while in the presence of an appropriate helpervirus or in a cell line containing appropriate sequences enablingencapsidation without coincident production of a contaminating helpervirus. As described below, a helper virus is not required for theproduction of the recombinant retrovirus of the disclosure, since thesequences for encapsidation are provided in the genome thus providing areplication competent retroviral vector for gene delivery or therapy.

Other existing replication competent retroviral vectors also tend to beunstable and lose sequences during horizontal or vertical transmissionto an infected cell or host cell and during replication. This may be duein-part from the presence of extra nucleotide sequences that includerepeats or which reduce the efficiency of a polymerase.

The retroviral genome and the proviral DNA of the disclosure have atleast three genes: the gag, the pol, and the env, these genes may beflanked by one or two long terminal (LTR) repeat, or in the provirus areflanked by two long terminal repeat (LTR) and sequences containingcis-acting sequences such as psi. The gag gene encodes the internalstructural (matrix, capsid, and nucleocapsid) proteins; the pol geneencodes the RNA-directed DNA polymerase (reverse transcriptase),protease and integrase; and the env gene encodes viral envelopeglycoproteins. The 5′ and/or 3′ LTRs serve to promote transcription andpolyadenylation of the virion RNAs. The LTR contains all othercis-acting sequences necessary for viral replication. Lentiviruses haveadditional genes including vif, vpr, tat, rev, vpu, nef, and vpx (inHIV-1, HIV-2 and/or SIV).

Adjacent to the 5′ LTR are sequences necessary for reverse transcriptionof the genome (the tRNA primer binding site) and for efficientencapsidation of viral RNA into particles (the Psi site). If thesequences necessary for encapsidation (or packaging of retroviral RNAinto infectious virion) are missing from the viral genome, the result isa cis defect which prevents encapsidation of genomic viral RNA. Thistype of modified vector is what has typically been used in prior genedelivery systems (i.e., systems lacking elements which are required forencapsidation of the virion) as ‘helper’ elements providing viralproteins in trans that package a non-replicating, but packageable, RNAgenome.

In a first embodiment, the disclosure provides a recombinant retroviruscapable of infecting a non-dividing cell, a dividing cell, or a cellhaving a cell proliferative disorder. The recombinant replicationcompetent retrovirus of the disclosure comprises a polynucleotidesequence encoding a viral GAG, a viral POL, a viral ENV, a heterologouspolynucleotide preceded by an internal ribosome entry site (IRES)encapsulated within a virion.

The phrase “non-dividing” cell refers to a cell that does not go throughmitosis. Non-dividing cells may be blocked at any point in the cellcycle, (e.g., G₀/G₁, G_(1/S), G_(2/M)), as long as the cell is notactively dividing. For ex vivo infection, a dividing cell can be treatedto block cell division by standard techniques used by those of skill inthe art, including, irradiation, aphidocolin treatment, serumstarvation, and contact inhibition. However, it should be understoodthat ex vivo infection is often performed without blocking the cellssince many cells are already arrested (e.g., stem cells). For example, arecombinant lentivirus vector is capable of infecting non-dividingcells. Examples of pre-existing non-dividing cells in the body includeneuronal, muscle, liver, skin, heart, lung, and bone marrow cells, andtheir derivatives. For dividing cells onco-retroviral vectors can beused.

By “dividing” cell is meant a cell that undergoes active mitosis, ormeiosis. Such dividing cells include stem cells, skin cells (e.g.,fibroblasts and keratinocytes), gametes, and other dividing cells knownin the art. Of particular interest and encompassed by the term dividingcell are cells having cell proliferative disorders, such as neoplasticcells. The term “cell proliferative disorder” refers to a conditioncharacterized by an abnormal number of cells. The condition can includeboth hypertrophic (the continual multiplication of cells resulting in anovergrowth of a cell population within a tissue) and hypotrophic (a lackor deficiency of cells within a tissue) cell growth or an excessiveinflux or migration of cells into an area of a body. The cellpopulations are not necessarily transformed, tumorigenic or malignantcells, but can include normal cells as well. Cell proliferativedisorders include disorders associated with an overgrowth of connectivetissues, such as various fibrotic conditions, including scleroderma,arthritis and liver cirrhosis. Cell proliferative disorders includeneoplastic disorders such as head and neck carcinomas. Head and neckcarcinomas would include, for example, carcinoma of the mouth,esophagus, throat, larynx, thyroid gland, tongue, lips, salivary glands,nose, paranasal sinuses, nasopharynx, superior nasal vault and sinustumors, esthesioneuroblastoma, squamous cell cancer, malignant melanoma,sinonasal undifferentiated carcinoma (SNUC), brain (includingglioblastomas) or blood neoplasia. Also included are carcinoma's of theregional lymph nodes including cervical lymph nodes, prelaryngeal lymphnodes, pulmonary juxtaesophageal lymph nodes and submandibular lymphnodes (Harrison's Principles of Internal Medicine (eds., Isselbacher, etal., McGraw-Hill, Inc., 13th Edition, pp 1850-1853, 1994). Other cancertypes, include, but are not limited to, lung cancer, colon-rectumcancer, breast cancer, prostate cancer, urinary tract cancer, uterinecancer lymphoma, oral cancer, pancreatic cancer, leukemia, melanoma,stomach cancer, skin cancer and ovarian cancer. The cell proliferativedisease also includes rheumatoid arthritis (O'Dell NEJM 350:2591 2004)and other auto-immune disorders (Mackay et al NEJM 345:340 2001) thatare often characterized by inappropriate proliferation of cells of theimmune system.

The heterologous nucleic acid sequence is operably linked to an IRES. Asused herein, the term “heterologous” nucleic acid sequence or transgenerefers to (i) a sequence that does not normally exist in a wild-typeretrovirus, (ii) a sequence that originates from a foreign species, or(iii) if from the same species, it may be substantially modified fromits original form. Alternatively, an unchanged nucleic acid sequencethat is not normally expressed in a cell is a heterologous nucleic acidsequence.

Depending upon the intended use of the retroviral vector of thedisclosure any number of heterologous polynucleotide or nucleic acidsequences may be inserted into the retroviral vector. For example, forin vitro studies commonly used marker genes or reporter genes may beused, including, antibiotic resistance and fluorescent molecules (e.g.,GFP). Additional polynucleotide sequences encoding any desiredpolypeptide sequence may also be inserted into the vector of thedisclosure. Where in vivo delivery of a heterologous nucleic acidsequence is sought both therapeutic and non-therapeutic sequences may beused. For example, the heterologous sequence can encode a therapeuticmolecule including antisense molecules (miRNA, siRNA) or ribozymesdirected to a particular gene associated with a cell proliferativedisorder or other gene-associated disease or disorder, the heterologoussequence can be a suicide gene (e.g., HSV-tk or PNP or cytosinedeaminase; either modified or unmodified), a growth factor or atherapeutic protein (e.g., Factor IX, IL2, and the like). Othertherapeutic proteins applicable to the disclosure are easily identifiedin the art.

In one embodiment, the heterologous polynucleotide within the vectorcomprises a cytosine deaminase that has been optimized for expression ina human cell. In a further embodiment, the cytosine deaminase comprisesa sequence that has been human codon optimized and comprises mutationsthat increase the cytosine deaminase's stability (e.g., reduceddegradation or increased thermo-stability) compared to a wild-typecytosine deaminase. In yet another embodiment, the heterologouspolynucleotide encodes a fusion construct comprising a cytosinedeaminase (either human codon optimized or non-optimized, either mutatedor non-mutated) operably linked to a polynucleotide encoding apolypeptide having UPRT or OPRT activity. In another embodiment, theheterologous polynucleotide comprises a CD polynucleotide of thedisclosure (e.g., SEQ ID NO:3, 5, 11, 13, 15, or 17).

In another embodiment, replication competent retroviral vector cancomprise a heterologous polynucleotide encoding a polypeptide comprisinga cytosine deaminase (as described herein) and may further comprise apolynucleotide comprising a miRNA or siRNA molecule either as part ofthe primary transcript from the viral promoter or linked to a promoter,which can be cell-type or tissue specific.

MicroRNAs (miRNA) are small, non-coding RNAs. They are located withinintrons of coding or non-coding gene, exons of non-coding genes or ininter-genic regions. miRNA genes are transcribed by RNA polymerase IIthat generate precursor polynucleotides called primary precursor miRNA(pri-miRNA). The pri-miRNA in the nucleus is processed by theribonuclease Drosha to produce the miRNA precursor (pre-miRNA) thatforms a short hairpin structure. Subsequently, pre-miRNA is transportedto the cytoplasm via Exportin 5 and further processed by anotherribonuclease called Dicer to generate an active, mature miRNA.

A mature miRNA is approximately 21 nucleotides in length. It exerts infunction by binding to the 3′ untranslated region of mRNA of targetedgenes and suppressing protein expression either by repression of proteintranslation or degradation of mRNA. miRNA are involved in biologicalprocesses including development, cell proliferation, differentiation andcancer progression. Studies of miRNA profiling indicate that some miRNAexpressions are tissue specific or enriched in certain tissues. Forexample, miR-142-3p, miR-181 and miR-223 expressions have demonstratedto be enriched in hematopoietic tissues in human and mouse (Baskervilleet al., 2005 RNA 11, 241-247; Chen et al., 2004 Science 303, 83-86).

Some miRNAs have been observed to be up-regulated (oncogenic miRNA) ordown-regulated (repressor) in several tumors (Spizzo et al., 2009 Cell137, 586el). For example, miR-21 is overexpressed in glioblastoma,breast, lung, prostate, colon, stomach, esophageal, and cervical cancer,uterine leiomyosarcoma, DLBCL, head and neck cancer. In contrast,members of let-7 have reported to be down-regulated in glioblastoma,lung, breast, gastric, ovary, prostate and colon cancers.Re-establishment of homeostasis of miRNA expression in cancer is animperative mechanism to inhibit or reverse cancer progression.

As a consequence of the vital functions modulated by miRNAs in cancers,focus in developing potential therapeutic approaches has been directedtoward antisense-mediated inhibition (antigomers) of oncogenic miRNAs.However, miRNA replacement might represent an equally efficaciousstrategy. In this approach, the most therapeutically useful miRNAs arethe ones expressed at low levels in tumors but at high level, andtherefore tolerated, in normal tissues.

miRNAs that are down-regulated in cancers could be useful as anticanceragents. Examples include mir-128-1, let-7, miR-26, miR-124, and miR-137(Esquela-Kerscher et al., 2008 Cell Cycle 7, 759-764; Kumar et al., 2008Proc Natl Acad Sci USA 105, 3903-3908; Kota et al., 2009 Cell 137,1005-1017; Silber et al., 2008 BMC Medicine 6:14 1-17). miR-128expression has reported to be enriched in the central nervous system andhas been observed to be down-regulated in glioblastomas (Sempere et al.,2004 Genome Biology 5:R13.5-11; Godlewski et al., 2008 Cancer Res 68:(22) 9125-9130). miR-128 is encoded by two distinct genes, miR-128-1 andmiR-128-2. Both are processed into identical mature sequence. Bmi-1 andE2F3a have been reported to be the direct targets of miR-128 (Godlewskiet al., 2008 Cancer Res 68: (22) 9125-9130; Zhang et al., 2009 J. MolMed 87:43-51). In addition, Bmi-1 expression has been observed to beup-regulated in a variety of human cancers, including gliomas, mantlecell lymphomas, non-small cell lung cancer B-cell non-Hodgkin'slymphoma, breast, colorectal and prostate cancer. Furthermore, Bmi-1 hasbeen demonstrated to be required for the self-renewal of stem cells fromdiverse tissues, including neuronal stem cells as well as “stem-like”cell population in gliomas.

Although there have been a number of in vitro demonstrations of thepossibilities of miRNA mediated inhibition of cellular function, it hasbeen difficult to deliver these as oligonucleotides or in viral vectorsas efficiently as necessary to have in vivo effects (e.g. Li et al. CellCycle 5:2103-2109 2006), as has been true for other molecules.Non-replicative vectors do not appear to be efficient enough in any caseto achieve delivery of a therapeutic gene into a significant portion oftumors. However it is also not simple to see how to use replicativevectors to deliver miRNA types of agents. In particular it is not clearhow to incorporate extra RNA sequences into the RNA genome ofreplication competent retroviruses and maintain the replicationefficiency and keep the addition stably incorporated into the genome.

Replication-defective retroviral and lentiviral vectors have been usedto stably express pri-mi RNA by a polymerase II promoter such as CMV orLTR and demonstrated production of mature miRNA. However, these vectorsdo not have to go through the entire lifecycle of the retrovirus orlentivirus multiple times as is required for replicating vectors. Thegenome has to be able to accommodate many more events than simple entry,integration and transcription. The concerns associated with the use of aRNA-based virus to express miRNA include: (1) the integrity of the viralRNA genome at post transcriptional step during RNA processing; (2) thestability of the inserted cassette during replication; and (3) properprocessing of pri-miRNA as part of the viral RNA transcribed from theLTR promoter producing mature miRNA.

Thus, incorporation of type III RNA polymerase III promoters such as theU6 and the H1 promoter in non-replicative retroviral and lentiviralvectors has been used widely to express functional small interferenceRNA (siRNA) producing a short hairpin structured RNA (Bromberg-White etal., 2004 J Virol 78:9, 4914-4916; Sliva et al., 2006 Virology 351,218-225; Haga et al., 2006, Transplant Proc 38(10):3184-8). The loopsequence is cleaved by Dicer producing the mature siRNAs that are 21-22nucleotides in length. shRNA can be stably expressed in cells todown-regulate target gene expression. However the incorporation of suchcassettes into the recombinant replication competent retroviral vector,the expression and the processing by Dicer to produce mature miRNAremain problematic.

In one embodiment, the disclosure provides a recombinant replicationcompetent retroviral vector that contains a heterologous polynucleotidesequence of a primary precursor miRNA.

In a further embodiment the primary precursor miRNA is of human origin.In another embodiment the primary precursor RNA sequence is downstreamof the env gene.

In another embodiment, the disclosure provides a recombinant replicationcompetent retroviral vector that contains a heterologous polynucleotidesequence of the human primary precursor miR-128-2 (SEQ ID NO:32)downstream of the env gene. miRNAs that are down-regulated in cancerscan be incorporated into the vector for therapeutic gene delivery. Forexample, let-7, miR-26, miR-124, and miR-137 (Esquela-Kerscher et al.,2008 Cell Cycle 7, 759-764; Kumar et al., 2008 Proc Natl Acad Sci USA105, 3903-3908; Kota et al., 2009 Cell 137, 1005-1017; Silber et al.,2008 BMC Medicine 6:14 1-17).

In yet another embodiment, the disclosure provides a recombinantreplication competent retroviral vector that contains a heterologouspolynucleotide sequence of the short hairpin structured humanpre-miR-128 linked to a human H1 promoter (SEQ ID NO: 33 and SEQ IDNO:34) downstream of the env gene. miRNAs that are down-regulated incancers can be incorporated into the vector for therapeutic genedelivery. For example, let-7, miR-26, miR-124, and miR-137(Esquela-Kerscher et al., 2008 Cell Cycle 7, 759-764; Kumar et al., 2008Proc Natl Acad Sci USA 105, 3903-3908; Kota et al., 2009 Cell 137,1005-1017; Silber et al., 2008 BMC Medicine 6:14 1-17).

Antisense nucleic acids are DNA or RNA molecules that are complementaryto at least a portion of a specific mRNA molecule (Weintraub, ScientificAmerican, 262:40, 1990). In the cell, the antisense nucleic acidshybridize to the corresponding mRNA, forming a double-stranded molecule.The antisense nucleic acids interfere with the translation of the mRNA,since the cell will not translate a mRNA that is double-stranded.Antisense oligomers of about 15 nucleotides are preferred, since theyare easily synthesized and are less likely to cause problems than largermolecules when introduced into the target cell. The use of antisensemethods to inhibit the in vitro translation of genes is well known inthe art (Marcus-Sakura, Anal. Biochem., 172:289, 1988).

The antisense nucleic acid can be used to block expression of a mutantprotein or a dominantly active gene product, such as amyloid precursorprotein that accumulates in Alzheimer's disease. Such methods are alsouseful for the treatment of Huntington's disease, hereditaryParkinsonism, and other diseases. Of particular interest are theblocking of genes associated with cell-proliferative disorders.Antisense nucleic acids are also useful for the inhibition of expressionof proteins associated with toxicity.

Use of an oligonucleotide to stall transcription is known as the triplexstrategy since the oligomer winds around double-helical DNA, forming athree-strand helix. Therefore, these triplex compounds can be designedto recognize a unique site on a chosen gene (Maher, et al., AntisenseRes. and Dev., 1(3):227, 1991; Helene, C., Anticancer Drug Design,6(6):569, 1991).

Ribozymes are RNA molecules possessing the ability to specificallycleave other single-stranded RNA in a manner analogous to DNArestriction endonucleases. Through the modification of nucleotidesequences which encode these RNAs, it is possible to engineer moleculesthat recognize specific nucleotide sequences in an RNA molecule andcleave it (Cech, J. Amer. Med. Assn., 260:3030, 1988). A major advantageof this approach is that, because they are sequence-specific, only mRNAswith particular sequences are inactivated.

As used herein, the term “RNA interference” (RNAi) refers to the processof sequence-specific post-transcriptional gene silencing mediated byshort interfering nucleic acids (siRNAs or microRNAs (miRNA)). The term“agent capable of mediating RNA interference” refers to siRNAs as wellas DNA and RNA vectors that encode siRNAs when transcribed within acell. The term siRNA or miRNA is meant to encompass any nucleic acidmolecule that is capable of mediating sequence specific RNAinterference, for example short interfering RNA (siRNA), double-strandedRNA (dsRNA), microRNA (miRNA), short hairpin RNA (shRNA), shortinterfering oligonucleotide, short interfering nucleic acid, shortinterfering modified oligonucleotide, chemically-modified siRNA,post-transcriptional gene silencing RNA (ptgsRNA), and others.

Suitable range for designing stem lengths of a hairpin duplex, includesstem lengths of 20-30 nucleotides, 30-50 nucleotides, 50-100nucleotides, 100-150 nucleotides, 150-200 nucleotides, 200-300nucleotides, 300-400 nucleotides, 400-500 nucleotides, 500-600nucleotides, and 600-700 nucleotides. Suitable range for designing looplengths of a hairpin duplex, includes loop lengths of 4-25 nucleotides,25-50 nucleotides, or longer if the stem length of the hair duplex issubstantial. In certain context, hairpin structures with duplexedregions that are longer than 21 nucleotides may promote effectivesiRNA-directed silencing, regardless of the loop sequence and length.

The replicating retroviral vectors of the disclosure can be used totreat disease by expressing engineered siRNA or miRNA (Dennis, Nature,418: 122 2002) that switches off or lowers expression of key genes thatgovern the proliferation or survival of diseased cells including tumorcells. Such targets include genes like Rad 51 a central enzyme in DNArepair, and without which cell growth is drastically restricted. Othertargets include many of the signaling pathway molecules that controlcell growth (Marquez & McCaffrey Hum Gene Ther. 19:27 2008). The siRNAor miRNA may be combined with expression of a cytotoxic gene from thesame or different retroviral vector of the disclosure. An example of asuitable cytotoxic gene comprise a cytosine deaminase or modifiedcytosine deaminase of the disclosure. Examples of siRNA or miRNA thatcan be expressed from the same vector or a different vector withcytosine deaminase are siRNA or miRNA's that target Thymidilatesynthase, Dihydropyrimidine dehydrogenase or other nucleic acid anabolicor synthetic enzymes, that can enhance or complement the action of 5-FUproduced locally in a tumor or tissue from 5-FC activation by cytosinedeaminase.

In use, the retroviral vector(s) will replicate through the tumor orother target tissue and before growth inhibition occurs the virus firstintegrates into the host genome and continues to make virus after growthof that cell is inhibited. Methods for selecting functional miRNA orsiRNA sequences are known in the art. Key feature in general indesigning effective siRNA or miRNA sequences is usually avoiding“off-target” effects. However for the use of replicating vectors thatare highly specific to tumor cells such as those of the disclosure,these side effects are not very important, as the cells are expected toeventually die. A retroviral vector of this disclosure can be made usingcells from other species for which the corresponding protein is notsignificantly targeted. Such cells include dog cell lines or chickencell line. Alternatively the virus is made by transient transfection onhuman 293 derived cells or other cell line that allows efficienttransient transfection. For this use the virus does not need to utilizean IRES, and the siRNA or miRNA sequence can simply be inserted at aconvenient site on the viral genome. This site includes the regiondownstream of the envelope and upstream of the 3′LTR of the replicatingretrovirus. Alternatively polIII transcription units can be inserted inthe viral genome with the appropriate siRNA or miRNA's, typicallydownstream of the 3′ envelope gene. Several different siRNA or miRNAsequences can be inserted to ensure efficient down regulation of thetarget gene or down regulation of more than one gene. Suitable sequencesand targets can be obtained from sources known to those skilled in theart. For example:

The MIT/ICBP siRNA Database http:(//)web.mit.edu/sirna/—“The MIT[Massachusetts Institute of Technology]/ICBP [Integrative Cancer BiologyProgram] siRNA Database is a university-wide effort to catalog theseexperimentally validated reagents and make that information available toother researchers, both within and outside the MIT community.(Massachusetts Institute of Technology).

RNAi Central—http:(//)katandin.cshl.org:9331/RNAi_web/scripts/main2.plRNAi resources, including siRNA and shRNA design tools. (Hannon Lab,Cold Spring Harbor Laboratory)

The RNAi Web—http:(//)www.rnaiweb.com/General resource.

siDIRECT—http:(//)genomics.jp/sidirect/Online target-specific siRNAdesign program for mammalian RNA interference. (University of Tokyo,Japan).

siRNA Database—A comprehensive siRNA database that contains siRNAtargets against all known mRNA sequences throughout a variety oforganisms. (Part of the Protein Lounge systems biology Web site)

siRNA Database and Resources for RNA Interference Studieshttp:(//)www.rnainterference.org/

siRNA Selector—http:(//)bioinfo.wistar.upenn.edu/siRNA/siRNA.htm. A setof rules was used for evaluating siRNA functionality based onthermodynamics parameters (Khvorova et al., 2003, Schwarz et al., 2003)and sequence-related determinants developed by Dharmacon (Reynolds etal., 2004). Specificity is determined using BLAST against UniGenedatabases. (Wistar Institute)

siRNA Target Finderhttp:(//)www(.)ambion.com/techlib/misc/siRNA_finder.html (Ambion).

The replicating retroviruses of the disclosure can also express targetsfor naturally occurring siRNA's that are restricted in expression toparticular cell types so that replication of the vector is significantlyinhibited in those cell types. The generation of murine leukemiavirus-based recombinant replication competent retroviral vector allowshigh level of transduction and thus high efficiency of gene delivery invivo. One major concern of using replication competent retroviral vectorhas been the uncontrolled spread of virus as reported previously(Donahue et al., J. Exp Med. 1992, 176:1124-1135; Calmes et al., Blood2005, 106: 2530-2533; Seggewiss et al., Blood 2006, 107: 3865-3867).Because of the nature of the virus, the viral spread may be achievedinitially within lymphatic cells and subsequently spread to peripheraltissues. For anti-tumor purposes some normal cells in the body that arenaturally replicating at some level are hematopoietic cells, cells ofthe lining of the gut, and some endothelial cells. These are thenpotential sites where virus that is in the circulation couldproductively infect. In general this would be undesirable. Any strayinfection of cells such as these can be inhibited by including a targetfor naturally occurring miRNA's or for a combination of miRNA's in thesecell types. Some feasibility of using miRNA targets to suppress immuneresponses has already been shown. (Brown et al. Nat Biotechnol. 200725:1457-67). These targets are small RNA sequences with a homologousmatch to the miRNA sequences that are naturally occurring. Thesesequences can be inserted in any convenient site in the vectors of thedisclosure without, in general significant deleterious consequence forvector viability, other than in a cell of the type desired. Vectors canbe made and used as described herein.

In one embodiment, the disclosure provides a recombinant replicationcompetent retroviral vector that contains a single copy of themiR-142-3p target sequence (142-3pT, SEQ ID NO:35) downstream of thetransgene, such as yCD2 or GFP, linked to the IRES. In addition tomiR181 and miR-223, the target sequence of other tissue or cell-enrichedmiRNA can be incorporated into the vector to restrict viral spread inspecific tissue or cell type manner. For example, miR-133 and miR206expressions are highly enriched in muscle cells (Kelly et al., 2008Nature Medicine 14:11 1278-1283.

In another embodiment, the disclosure provides a recombinant replicationcompetent retroviral vector that contains 4 copies of the 142-3pT (SEQID NO: 36) downstream of the transgene, such as yCD2 or GFP, linked tothe IRES. In addition to miR181 and miR-223, the target sequence ofother tissue or cell-enriched miRNA can be incorporated into the vectorto restrict viral spread in specific tissue or cell type manner. Forexample, miR-133 and miR206 expressions are highly enriched in musclecells. The disclosure provides flexibility of single, multiple orcombination of target sequence of miRNA and thereby provides restrictionof uncontrolled viral spread in a tissue- and/or cell-specific fashionin vitro and in vivo (e. g. hematopoietic and/or muscle cells), (Kellyet al., 2008 Nature Medicine 14:11 1278-1283).

The miRNA target can be inserted 3′ to the transgene but before the3′LTR or upstream of the IRES but after the 3′ end of the envelope. Ingeneral the target would not be inserted into protein coding sequences.

In yet further embodiments, the heterologous polynucleotide may comprisea cytokine such as an interleukin, interferon gamma or the like.Cytokines that may expressed from a retroviral vector of the disclosureinclude, but are not limited to, IL-1alpha, IL-1beta, IL-2, IL-3, IL-4,IL-5, IL-6, IL-7, IL-8, IL-9, IL-10, IL-11, IL-12, IL-13, IL-14, IL-15,IL-16, IL-17, IL-18, IL-19, IL-20, and IL-21, anti-CD40, CD40L,IFN-gamma and TNF-alpha, soluble forms of TNF-alpha, lymphotoxin-alpha(LT-alpha, also known as TNF-beta), LT-beta (found in complexheterotrimer LT-alpha2-beta), OPGL, FasL, CD27L, CD30L, CD40L, 4-1BBL,DcR3, OX40L, TNF-gamma (International Publication No. WO 96/14328),AIM-I (International Publication No. WO 97/33899), endokine-alpha(International Publication No. WO 98/07880), OPG, and neutrokine-alpha(International Publication No. WO 98/18921, OX40, and nerve growthfactor (NGF), and soluble forms of Fas, CD30, CD27, CD40 and 4-IBB, TR2(International Publication No. WO 96/34095), DR3 (InternationalPublication No. WO 97/33904), DR4 (International Publication No. WO98/32856), TR5 (International Publication No. WO 98/30693), TRANK, TR9(International Publication No. WO 98/56892), TR10 (InternationalPublication No. WO 98/54202), 312C2 (International Publication No. WO98/06842), and TR12, and soluble forms CD154, CD70, and CD153.Angiogenic proteins may be useful in some embodiments, particularly forprotein production from cell lines. Such angiogenic factors include, butare not limited to, Glioma Derived Growth Factor (GDGF), PlateletDerived Growth Factor-A (PDGF-A), Platelet Derived Growth Factor-B(PDGF-B), Placental Growth Factor (PIGF), Placental Growth Factor-2(PIGF-2), Vascular Endothelial Growth Factor (VEGF), VascularEndothelial Growth Factor-A (VEGF-A), Vascular Endothelial GrowthFactor-2 (VEGF-2), Vascular Endothelial Growth Factor B (VEGF-3),Vascular Endothelial Growth Factor B-1 86 (VEGF-B186), VascularEndothelial Growth Factor-D (VEGF-D), Vascular Endothelial GrowthFactor-D (VEGF-D), and Vascular Endothelial Growth Factor-E (VEGF-E).Fibroblast Growth Factors may be delivered by a vector of the disclosureand include, but are not limited to, FGF-1, FGF-2, FGF-3, FGF-4, FGF-5,FGF-6, FGF-7, FGF-8, FGF-9, FGF-10, FGF-11, FGF-12, FGF-13, FGF-14, andFGF-15. Hematopoietic growth factors may be delivered using vectors ofthe disclosure, such growth factors include, but are not limited to,granulocyte macrophage colony stimulating factor (GM-CSF)(sargramostim), granulocyte colony stimulating factor (G-CSF)(filgrastim), macrophage colony stimulating factor (M-CSF, CSF-1)erythropoietin (epoetin alfa), stem cell factor (SCF, c-kit ligand,steel factor), megakaryocyte colony stimulating factor, PIXY321 (aGMCSF/IL-3) fusion protein and the like.

Generally, the recombinant virus of the disclosure is capable oftransferring a nucleic acid sequence into a target cell.

The term “regulatory nucleic acid sequence” refers collectively topromoter sequences, polyadenylation signals, transcription terminationsequences, upstream regulatory domains, origins of replication,enhancers and the like, which collectively provide for the replication,transcription and translation of a coding sequence in a recipient cell.Not all of these control sequences need always be present so long as theselected coding sequence is capable of being replicated, transcribed andtranslated in an appropriate host cell. One skilled in the art canreadily identify regulatory nucleic acid sequence from public databasesand materials. Furthermore, one skilled in the art can identify aregulatory sequence that is applicable for the intended use, forexample, in vivo, ex vivo, or in vitro.

An internal ribosome entry sites (“IRES”) refers to a segment of nucleicacid that promotes the entry or retention of a ribosome duringtranslation of a coding sequence usually 3′ to the IRES. In someembodiments the IRES may comprise a splice acceptor/donor site, however,preferred IRESs lack a splice acceptor/donor site. Normally, the entryof ribosomes into messenger RNA takes place via the cap located at the5′ end of all eukaryotic mRNAs. However, there are exceptions to thisuniversal rule. The absence of a cap in some viral mRNAs suggests theexistence of alternative structures permitting the entry of ribosomes atan internal site of these RNAs. To date, a number of these structures,designated IRES on account of their function, have been identified inthe 5′ noncoding region of uncapped viral mRNAs, such as that, inparticular, of picornaviruses such as the poliomyelitis virus (Pelletieret al., 1988, Mol. Cell. Biol., 8, 1103-1112) and the EMCV virus(encephalo-myocarditis virus (Jang et al., J. Virol., 1988, 62,2636-2643). The disclosure provides the use of an IRES in the context ofa replication-competent retroviral vector.

The term “promoter region” is used herein in its ordinary sense to referto a nucleotide region comprising a DNA regulatory sequence, wherein theregulatory sequence is derived from a gene which is capable of bindingRNA polymerase and initiating transcription of a downstream(3′-direction) coding sequence. The regulatory sequence may behomologous or heterologous to the desired gene sequence. For example, awide range of promoters may be utilized, including viral or mammalianpromoter as described above.

The heterologous nucleic acid sequence is typically under control ofeither the viral LTR promoter-enhancer signals or an internal promoter,and retained signals within the retroviral LTR can still bring aboutefficient integration of the vector into the host cell genome.Accordingly, the recombinant retroviral vectors of the disclosure, thedesired sequences, genes and/or gene fragments can be inserted atseveral sites and under different regulatory sequences. For example, asite for insertion can be the viral enhancer/promoter proximal site(i.e., 5′ LTR-driven gene locus). Alternatively, the desired sequencescan be inserted into a regulatory sequence distal site (e.g., the IRESsequence 3′ to the env gene) or where two or more heterologous sequencesare present one heterologous sequence may be under the control of afirst regulatory region and a second heterologous sequence under thecontrol of a second regulatory region. Other distal sites include viralpromoter sequences, where the expression of the desired sequence orsequences is through splicing of the promoter proximal cistron, aninternal heterologous promoter as SV40 or CMV, or an internal ribosomeentry site (IRES) can be used.

In one embodiment, the retroviral genome of the disclosure contains anIRES comprising a cloning site downstream of the IRES for insertion of adesired/heterologous polynucleotide. In one embodiment, the IRES islocated 3′ to the env gene in the retroviral vector, but 5′ to thedesired heterologous polynucleotide. Accordingly, a heterologouspolynucleotide encoding a desired polypeptide may be operably linked tothe IRES.

In another embodiment, a targeting polynucleotide sequence is includedas part of the recombinant retroviral vector of the disclosure. Thetargeting polynucleotide sequence is a targeting ligand (e.g., peptidehormones such as heregulin, a single-chain antibodies, a receptor or aligand for a receptor), a tissue-specific or cell-type specificregulatory element (e.g., a tissue-specific or cell-type specificpromoter or enhancer), or a combination of a targeting ligand and atissue-specific/cell-type specific regulatory element. Preferably, thetargeting ligand is operably linked to the env protein of theretrovirus, creating a chimeric retroviral env protein. The viral GAG,viral POL and viral ENV proteins can be derived from any suitableretrovirus (e.g., MLV or lentivirus-derived). In another embodiment, theviral ENV protein is non-retrovirus-derived (e.g., CMV or VSV).

In one embodiment, the recombinant retrovirus of the disclosure isgenetically modified in such a way that the virus is targeted to aparticular cell type (e.g., smooth muscle cells, hepatic cells, renalcells, fibroblasts, keratinocytes, mesenchymal stem cells, bone marrowcells, chondrocyte, epithelial cells, intestinal cells, mammary cells,neoplastic cells, glioma cells, neuronal cells and others known in theart) such that the recombinant genome of the retroviral vector isdelivered to a target non-dividing, a target dividing cell, or a targetcell having a cell proliferative disorder.

In one embodiment, the retroviral vector is targeted to the cell bybinding to cells having a molecule on the external surface of the cell.This method of targeting the retrovirus utilizes expression of atargeting ligand on the coat of the retrovirus to assist in targetingthe virus to cells or tissues that have a receptor or binding moleculewhich interacts with the targeting ligand on the surface of theretrovirus. After infection of a cell by the virus, the virus injectsits nucleic acid into the cell and the retrovirus genetic material canintegrate into the host cell genome.

In another embodiment, targeting uses cell- or tissue-specificregulatory elements to promote expression and transcription of the viralgenome in a targeted cell which actively utilizes the regulatoryelements, as described more fully below. The transferred retrovirusgenetic material is then transcribed and translated into proteins withinthe host cell. The targeting regulatory element is typically linked tothe 5′ and/or 3′ LTR, creating a chimeric LTR.

By inserting a heterologous polynucleotide of interest into the viralvector of the disclosure, along with another gene which encodes, forexample, the ligand for a receptor on a specific target cell, the vectoris now target specific. Viral vectors can be made target specific byattaching, for example, a sugar, a glycolipid, or a protein. Targetingcan be accomplished by using an antibody to target the viral vector.Those of skill in the art will know of, or can readily ascertain,specific polynucleotide sequences which can be inserted into the viralgenome or proteins which can be attached to a viral envelope to allowtarget specific delivery of the viral vector containing the nucleic acidsequence of interest.

Thus, the disclosure includes in one embodiment, a chimeric env proteincomprising a retroviral ENV protein operably linked to a targetingpolypeptide. The targeting polypeptide can be a cell specific receptormolecule, a ligand for a cell specific receptor, an antibody or antibodyfragment to a cell specific antigenic epitope or any other ligand easilyidentified in the art which is capable of binding or interacting with atarget cell. Examples of targeting polypeptides or molecules includebivalent antibodies using biotin-streptavidin as linkers (Etienne-Julanet al., J. Of General Virol., 73, 3251-3255 (1992); Roux et al., Proc.Natl. Acad. Sci USA 86, 9079-9083 (1989)), recombinant virus containingin its envelope a sequence encoding a single-chain antibody variableregion against a hapten (Russell et al., Nucleic Acids Research, 21,1081-1085 (1993)), cloning of peptide hormone ligands into theretrovirus envelope (Kasahara et al., Science, 266, 1373-1376 (1994)),chimeric EPO/env constructs (Kasahara et al., 1994), single-chainantibody against the low density lipoprotein (LDL) receptor in theecotropic MLV envelope, resulting in specific infection of HeLa cellsexpressing LDL receptor (Somia et al., Proc. Natl. Acad. Sci USA, 92,7570-7574 (1995)), similarly the host range of ALV can be altered byincorporation of an integrin ligand, enabling the virus to now crossspecies to specifically infect rat glioblastoma cells (Valsesia-Wittmannet al., J. Virol. 68, 4609-4619 (1994)), and Dornberg and co-workers(Chu and Dornburg, J. Virol 69, 2659-2663 (1995);M. Engelstadter et al.Gene Therapy 8, 1202-1206 (2001)) have reported tissue-specifictargeting of spleen necrosis virus (SNV), an avian retrovirus, usingenvelopes containing single-chain antibodies directed against tumormarkers.

The disclosure provides a method of producing a recombinant retroviruscapable of infecting a target cell comprising transfecting a suitablehost cell with the following: a vector comprising a polynucleotidesequence encoding a viral gag, a viral pol and a viral env, and aheterologous polynucleotide, operably linked to a regulatory nucleicacid sequence, and recovering the recombinant virus.

The retrovirus and methods of the disclosure provide a replicationcompetent retrovirus that does not require helper virus or additionalnucleic acid sequence or proteins in order to propagate and producevirion. For example, the nucleic acid sequences of the retrovirus of thedisclosure encode a group specific antigen and reverse transcriptase,(and integrase and protease-enzymes necessary for maturation and reversetranscription), respectively, as discussed above. The viral gag and polcan be derived from a lentivirus, such as HIV or an oncovirus orgammaretrovirus such as MoMLV. In addition, the nucleic acid genome ofthe retrovirus of the disclosure includes a sequence encoding a viralenvelope (ENV) protein. The env gene can be derived from anyretroviruses. The env may be an amphotropic envelope protein whichallows transduction of cells of human and other species, or may be anecotropic envelope protein, which is able to transduce only mouse andrat cells. Further, it may be desirable to target the recombinant virusby linkage of the envelope protein with an antibody or a particularligand for targeting to a receptor of a particular cell-type. Asmentioned above, retroviral vectors can be made target specific byinserting, for example, a glycolipid, or a protein. Targeting is oftenaccomplished by using an antibody to target the retroviral vector to anantigen on a particular cell-type (e.g., a cell type found in a certaintissue, or a cancer cell type). Those of skill in the art will know of,or can readily ascertain without undue experimentation, specific methodsto achieve delivery of a retroviral vector to a specific target. In oneembodiment, the env gene is derived from a non-retrovirus (e.g., CMV orVSV). Examples of retroviral-derived env genes include, but are notlimited to: Moloney murine leukemia virus (MoMuLV), Harvey murinesarcoma virus (HaMuSV), murine mammary tumor virus (MuMTV), gibbon apeleukemia virus (GaLV), human immunodeficiency virus (HIV) and RousSarcoma Virus (RSV). Other env genes such as Vesicular stomatitis virus(VSV) (Protein G), cytomegalovirus envelope (CMV), or influenza virushemagglutinin (HA) can also be used.

In one embodiment, the retroviral genome is derived from anonco-retrovirus, and more particularly a mammalian onco-retrovirus. In afurther embodiment, the retroviral genome is derived from a gammaretrovirus, and more particularly a mammalian gamma retrovirus. By“derived” is meant that the parent polynucleotide sequence is anwild-type oncovirus which has been modified by insertion or removal ofnaturally occurring sequences (e.g., insertion of an IRES, insertion ofa heterologous polynucleotide encoding a polypeptide or inhibitorynucleic acid of interest, swapping of a more effective promoter from adifferent retrovirus or virus in place of the wild-type promoter and thelike).

Unlike recombinant retroviruses produced by standard methods in the artthat are defective and require assistance in order to produce infectiousvector particles, the disclosure provides a retrovirus that isreplication-competent.

In another embodiment, the disclosure provides retroviral vectors thatare targeted using regulatory sequences. Cell- or tissue-specificregulatory sequences (e.g., promoters) can be utilized to targetexpression of gene sequences in specific cell populations. Suitablemammalian and viral promoters for the disclosure are described elsewhereherein. Accordingly, in one embodiment, the disclosure provides aretrovirus having tissue-specific promoter elements at the 5′ end of theretroviral genome. Typically, the tissue-specific regulatoryelements/sequences are in the U3 region of the LTR of the retroviralgenome, including for example cell- or tissue-specific promoters andenhancers to neoplastic cells (e.g., tumor cell-specific enhancers andpromoters), and inducible promoters (e.g., tetracycline).

Transcription control sequences of the disclosure can also includenaturally occurring transcription control sequences naturally associatedwith a gene encoding a superantigen, a cytokine or a chemokine.

In some circumstances, it may be desirable to regulate expression. Forexample, different viral promoters with varying strengths of activitymay be utilized depending on the level of expression desired. Inmammalian cells, the CMV immediate early promoter if often used toprovide strong transcriptional activation. Modified versions of the CMVpromoter that are less potent have also been used when reduced levels ofexpression of the transgene are desired. When expression of a transgenein hematopoietic cells is desired, retroviral promoters such as the LTRsfrom MLV or MMTV can be used. Other viral promoters that can be usedinclude SV40, RSV LTR, HIV-1 and HIV-2 LTR, adenovirus promoters such asfrom the E1A, E2A, or MLP region, AAV LTR, cauliflower mosaic virus,HSV-TK, and avian sarcoma virus.

Similarly tissue specific or selective promoters may be used to effecttranscription in specific tissues or cells so as to reduce potentialtoxicity or undesirable effects to non-targeted tissues. For example,promoters such as the PSA, probasin, prostatic acid phosphatase orprostate-specific glandular kallikrein (hK2) may be used to target geneexpression in the prostate. The Whey accessory protein (WAP) may be usedfor breast tissue expression (Andres et al., PNAS 84:1299-1303, 1987).Other promoters/regulatory domains that can be used are set forth inTable 1.

“Tissue-specific regulatory elements” are regulatory elements (e.g.,promoters) that are capable of driving transcription of a gene in onetissue while remaining largely “silent” in other tissue types. It willbe understood, however, that tissue-specific promoters may have adetectable amount of “background” or “base” activity in those tissueswhere they are silent. The degree to which a promoter is selectivelyactivated in a target tissue can be expressed as a selectivity ratio(activity in a target tissue/activity in a control tissue). In thisregard, a tissue specific promoter useful in the practice of thedisclosure typically has a selectivity ratio of greater than about 5.Preferably, the selectivity ratio is greater than about 15.

In certain indications, it may be desirable to activate transcription atspecific times after administration of the recombinant replicationcompetent retrovirus of the disclosure (RRCR). This may be done withpromoters that are hormone or cytokine regulatable. For example intherapeutic applications where the indication is a gonadal tissue wherespecific steroids are produced or routed to, use of androgen or estrogenregulated promoters may be advantageous. Such promoters that are hormoneregulatable include MMTV, MT-1, ecdysone and RuBisco. Other hormoneregulated promoters such as those responsive to thyroid, pituitary andadrenal hormones may be used. Cytokine and inflammatory proteinresponsive promoters that could be used include K and T Kininogen(Kageyama et al., 1987), c-fos, TNF-alpha, C-reactive protein (Arcone etal., 1988), haptoglobin (Oliviero et al., 1987), serum amyloid A2, C/EBPalpha, IL-1, IL-6 (Poli and Cortese, 1989), Complement C3 (Wilson etal., 1990), IL-8, alpha-1 acid glycoprotein (Prowse and Baumann, 1988),alpha-1 antitypsin, lipoprotein lipase (Zechner et al., 1988),angiotensinogen (Ron et al., 1990), fibrinogen, c-jun (inducible byphorbol esters, TNF-alpha, UV radiation, retinoic acid, and hydrogenperoxide), collagenase (induced by phorbol esters and retinoic acid),metallothionein (heavy metal and glucocorticoid inducible), Stromelysin(inducible by phorbol ester, interleukin-1 and EGF), alpha-2macroglobulin and alpha-1 antichymotrypsin. Tumor specific promoterssuch as osteocalcin, hypoxia-responsive element (HRE), MAGE-4, CEA,alpha-fetoprotein, GRP78/BiP and tyrosinase may also be used to regulategene expression in tumor cells.

In addition, this list of promoters should not be construed to beexhaustive or limiting, those of skill in the art will know of otherpromoters that may be used in conjunction with the promoters and methodsdisclosed herein.

TABLE 1 TISSUE SPECIFIC PROMOTERS Tissue Promoter Pancreas InsulinElastin Amylase pdr-1 pdx-1 glucokinase Liver Albumin PEPCK HBV enhancerα fetoprotein apolipoprotein C α-1 antitrypsin vitellogenin, NF-ABTransthyretin Skeletal muscle Myosin H chain Muscle creatine kinaseDystrophin Calpain p94 Skeletal alpha-actin fast troponin 1 Skin KeratinK6 Keratin K1 Lung CFTR Human cytokeratin 18 (K18) Pulmonary surfactantproteins A, B and C CC-10 P1 Smooth muscle sm22 α SM-alpha-actinEndothelium Endothelin-1 E-selectin von Willebrand factor TIE (Korhonenet al., 1995) KDR/flk-1 Melanocytes Tyrosinase Adipose tissueLipoprotein lipase (Zechner et al., 1988) Adipsin (Spiegelman et al.,1989) acetyl- CoA carboxylase (Pape and Kim, 1989) glycerophosphatedehydrogenase (Dani et al., 1989) adipocyte P2 (Hunt et al., 1986)Breast Whey Acidic Protien (WAP) (Andres et al. PNAS 84: 1299-1303 1987Blood β-globin

It will be further understood that certain promoters, while notrestricted in activity to a single tissue type, may nevertheless showselectivity in that they may be active in one group of tissues, and lessactive or silent in another group. Such promoters are also termed“tissue specific”, and are contemplated for use with the disclosure. Forexample, promoters that are active in a variety of central nervoussystem (CNS) neurons may be therapeutically useful in protecting againstdamage due to stroke, which may affect any of a number of differentregions of the brain. Accordingly, the tissue-specific regulatoryelements used in the disclosure, have applicability to regulation of theheterologous proteins as well as a applicability as a targetingpolynucleotide sequence in the present retroviral vectors.

In yet another embodiment, the disclosure provides plasmids comprising arecombinant retroviral derived construct. The plasmid can be directlyintroduced into a target cell or a cell culture such as NIH 3T3 or othertissue culture cells. The resulting cells release the retroviral vectorinto the culture medium.

The disclosure provides a polynucleotide construct comprising from 5′ to3′: a promoter or regulatory region useful for initiating transcription;a psi packaging signal; a gag encoding nucleic acid sequence, a polencoding nucleic acid sequence; an env encoding nucleic acid sequence;an internal ribosome entry site nucleic acid sequence; a heterologouspolynucleotide encoding a marker, therapeutic or diagnostic polypeptide;and a LTR nucleic acid sequence. As described elsewhere herein and asfollows the various segment of the polynucleotide construct of thedisclosure (e.g., a recombinant replication competent retroviralpolynucleotide) are engineered depending in part upon the desired hostcell, expression timing or amount, and the heterologous polynucleotide.A replication competent retroviral construct of the disclosure can bedivided up into a number of domains that may be individually modified bythose of skill in the art.

For example, the promoter can comprise a CMV promoter having a sequenceas set forth in SEQ ID NO:19, 20 or 22 from nucleotide 1 to aboutnucleotide 582 and may include modification to one or more (e.g., 2-5,5-10, 10-20, 20-30, 30-50, 50-100 or more nucleic acid bases) so long asthe modified promoter is capable of directing and initiatingtranscription. In one embodiment, the promoter or regulatory regioncomprises a CMV-R-U5 domain polynucleotide. The CMV-R-U5 domaincomprises the immediately early promoter from human cytomegalovirus tothe MLV R-U5 region. In one embodiment, the CMV-R-U5 domainpolynucleotide comprises a sequence as set forth in SEQ ID NO:19, 20 or22 from about nucleotide 1 to about nucleotide 1202 or sequences thatare at least 95% identical to a sequence as set forth in SEQ ID NO:19,20, or 22 wherein the polynucleotide promotes transcription of a nucleicacid molecule operably linked thereto. The gag domain of thepolynucleotide may be derived from any number of retroviruses, but willtypically be derived from an oncoretrovirus and more particularly from amammalian oncoretrovirus. In one embodiment the gag domain comprises asequence from about nucleotide number 1203 to about nucleotide 2819 or asequence having at least 95%, 98%, 99% or 99.8% (rounded to the nearest10^(th)) identity thereto. The pol domain of the polynucleotide may bederived from any number of retroviruses, but will typically be derivedfrom an oncoretrovirus and more particularly from a mammalianoncoretrovirus. In one embodiment the pol domain comprises a sequencefrom about nucleotide number 2820 to about nucleotide 6358 or a sequencehaving at least 95%, 98%, 99% or 99.9% (roundest to the nearest 10^(th))identity thereto. The env domain of the polynucleotide may be derivedfrom any number of retroviruses, but will typically be derived from anoncoretrovirus or gamma-retrovirus and more particularly from amammalian oncoretrovirus or gamma-retrovirus. In some embodiments theenv coding domain comprises an amphotropic env domain. In one embodimentthe env domain comprises a sequence from about nucleotide number 6359 toabout nucleotide 8323 or a sequence having at least 95%, 98%, 99% or99.8% (roundest to the nearest 10^(th)) identity thereto. The IRESdomain of the polynucleotide may be obtained from any number of internalribosome entry sites. In one embodiment, IRES is derived from anencephalomyocarditis virus. In one embodiment the IRES domain comprisesa sequence from about nucleotide number 8327 to about nucleotide 8876 ora sequence having at least 95%, 98%, or 99% (roundest to the nearest10th) identity thereto so long as the domain allows for entry of aribosome. The heterologous domain can comprise a cytosine deaminase ofthe disclosure. In one embodiment, the CD polynucleotide comprises ahuman codon optimized sequence. In yet another embodiment, the CDpolynucleotide encodes a mutant polypeptide having cytosine deaminase,wherein the mutations confer increased thermal stabilization thatincrease the melting temperature (Tm) by 10° C. allowing sustainedkinetic activity over a broader temperature range and increasedaccumulated levels of protein. In one embodiment, the cytosine deaminasecomprises a sequence as set forth in SEQ ID NO:19 or 22 from aboutnucleotide number 8877 to about 9353. The heterologous domain may befollowed by a polypurine rich domain. The 3′ LTR can be derived from anynumber of retroviruses, typically an oncoretrovirus and preferably amammalian oncoretrovirus. In one embodiment, the 3′ LTR comprises aU3-R-U5 domain. In yet another embodiment the LTR comprises a sequenceas set forth in SEQ ID NO:19 or 22 from about nucleotide 9405 to about9998 or a sequence that is at least 95%, 98% or 99.5% (rounded to thenearest 10^(th)) identical thereto.

The disclosure also provides a recombinant retroviral vector comprisingfrom 5′ to 3′ a CMV-R-U5, fusion of the immediate early promoter fromhuman cytomegalovirus to the MLV R-U5 region; a PBS, primer binding sitefor reverse transcriptase; a 5′ splice site; a ψ packaging signal; agag, ORF for MLV group specific antigen; a pol, ORF for MLV polymerasepolyprotein; a 3′ splice site; a 4070A env, ORF for envelope protein ofMLV strain 4070A; an IRES, internal ribosome entry site ofencephalomyocarditis virus; a modified cytosine deaminase(thermostabilized and codon optimized); a PPT, polypurine tract; and aU3-R-U5, MLV long terminal repeat. This structure is further depicted inFIG. 3.

The disclosure also provides a retroviral vector comprising a sequenceas set forth in SEQ ID NO:19, 20 or 22.

The retroviral vectors can be used to treat a wide range of disease anddisorders including a number of cell proliferative diseases anddisorders (see, e.g., U.S. Pat. Nos. 4,405,712 and 4,650,764; Friedmann,1989, Science, 244:1275-1281; Mulligan, 1993, Science, 260:926-932, R.Crystal, 1995, Science 270:404-410, each of which are incorporatedherein by reference in their entirety, see also, The Development ofHuman Gene Therapy, Theodore Friedmann, Ed., Cold Spring HarborLaboratory Press, Cold Spring Harbor, N.Y., 1999. ISBN 0-87969-528-5,which is incorporated herein by reference in its entirety).

The disclosure also provides gene therapy for the treatment of cellproliferative disorders. Such therapy would achieve its therapeuticeffect by introduction of an appropriate therapeutic polynucleotide(e.g., antisense, ribozymes, suicide genes, siRNA), into cells ofsubject having the proliferative disorder. Delivery of polynucleotideconstructs can be achieved using the recombinant retroviral vector ofthe disclosure, particularly if it is based on MLV, which is capable ofinfecting dividing cells.

In addition, the therapeutic methods (e.g., the gene therapy or genedelivery methods) as described herein can be performed in vivo or exvivo. It may be preferable to remove the majority of a tumor prior togene therapy, for example surgically or by radiation. In some aspects,the retroviral therapy may be preceded or followed by surgery,chemotherapy or radiation therapy.

Thus, the disclosure provides a recombinant retrovirus capable ofinfecting a non-dividing cell, a dividing cell or a neoplastic cell,therein the recombinant retrovirus comprises a viral GAG; a viral POL; aviral ENV; a heterologous nucleic acid operably linked to an IRES; andcis-acting nucleic acid sequences necessary for packaging, reversetranscription and integration. The recombinant retrovirus can be alentivirus, such as HIV, or can be an oncovirus. As described above forthe method of producing a recombinant retrovirus, the recombinantretrovirus of the disclosure may further include at least one of VPR,VIF, NEF, VPX, TAT, REV, and VPU protein. While not wanting to be boundby a particular theory, it is believed that one or more of thesegenes/protein products are important for increasing the viral titer ofthe recombinant retrovirus produced (e.g., NEF) or may be necessary forinfection and packaging of virion.

The disclosure also provides a method of nucleic acid transfer to atarget cell to provide expression of a particular nucleic acid (e.g., aheterologous sequence). Therefore, in another embodiment, the disclosureprovides a method for introduction and expression of a heterologousnucleic acid in a target cell comprising infecting the target cell withthe recombinant virus of the disclosure and expressing the heterologousnucleic acid in the target cell. As mentioned above, the target cell canbe any cell type including dividing, non-dividing, neoplastic,immortalized, modified and other cell types recognized by those of skillin the art, so long as they are capable of infection by a retrovirus.

It may be desirable to modulate the expression of a gene in a cell bythe introduction of a nucleic acid sequence (e.g., the heterologousnucleic acid sequence) by the method of the disclosure, wherein thenucleic acid sequence give rise, for example, to an antisense orribozyme molecule. The term “modulate” envisions the suppression ofexpression of a gene when it is over-expressed, or augmentation ofexpression when it is under-expressed. Where a cell proliferativedisorder is associated with the expression of a gene, nucleic acidsequences that interfere with the gene's expression at the translationallevel can be used. This approach utilizes, for example, antisensenucleic acid, ribozymes, or triplex agents to block transcription ortranslation of a specific mRNA, either by masking that mRNA with anantisense nucleic acid or triplex agent, or by cleaving it with aribozyme.

It may be desirable to transfer a nucleic acid encoding a biologicalresponse modifier (e.g., a cytokine) into a cell or subject. Included inthis category are immunopotentiating agents including nucleic acidsencoding a number of the cytokines classified as “interleukins”. Theseinclude, for example, interleukins 1 through 15, as well as otherresponse modifiers and factors described elsewhere herein. Also includedin this category, although not necessarily working according to the samemechanisms, are interferons, and in particular gamma interferon, tumornecrosis factor (TNF) and granulocyte-macrophage-colony stimulatingfactor (GM-CSF). Other polypeptides include, for example, angiogenicfactors and anti-angiogenic factors. It may be desirable to deliver suchnucleic acids to bone marrow cells or macrophages to treat enzymaticdeficiencies or immune defects. Nucleic acids encoding growth factors,toxic peptides, ligands, receptors, or other physiologically importantproteins can also be introduced into specific target cells.

The disclosure can be used for delivery of heterologous polynucleotidesthat promote drug specific targeting and effects. For example, HER2(see, e.g., SEQ ID NO:23 and 24), a member of the EGF receptor family,is the target for binding of the drug trastuzumab (Herceptin™,Genentech). Trastuzumab is a mediator of antibody-dependent cellularcytotoxicity (ADCC). Activity is preferentially targeted toHER2-expressing cells with 2+ and 3+ levels of overexpression byimmunohistochemistry rather than 1+ and non-expressing cells (Herceptinprescribing information, Crommelin 2002). Enhancement of expression ofHER2 by introduction of vector expressing HER2 or truncated HER2(expressing only the extracellular and transmembrane domains) in HER2low tumors may facilitate optimal triggering of ADCC and overcome therapidly developing resistance to Herceptin that is observed in clinicaluse.

The substitution of yCD2 (comprising SEQ ID NO:19 from about 8877 to9353) for the intracellular domain of HER2 allows for cell surfaceexpression of HER2 and cytosolic localization of yCD2. The HER2extracellular domain (ECD) and transmembrane Domain (TM) (approximately2026 bp from about position 175 to 2200 of SEQ ID NO:23) can beamplified by PCR (Yamamoto et al., Nature 319:230-234, 1986; Chen etal., Canc. Res., 58:1965-1971, 1998) or chemically synthesized (BioBasicInc., Markham, Ontario, Canada) and inserted between the IRES and yCD2gene in the vector pAC3-yCD2 SEQ ID NO: 19 (e.g., between aboutnucleotide 8876 and 8877 of SEQ ID NO:19). Alternatively, the yCD genecan be excised and replaced with a polynucleotide encoding a HER2polypeptide or fragment thereof. A further truncated HER2 with only theHerceptin binding domain IV of the ECD and TM domains (approximately 290bp from position 1910 to 2200) can be amplified or chemicallysynthesized and used as above (Landgraf 2007; Garrett et al., J. ofImmunol., 178:7120-7131, 2007). A further modification of this truncatedform with the native signal peptide (approximately 69 bp from position175-237) fused to domain IV and the TM can be chemically synthesized andused as above. The resulting viruses can be used to treat a cellproliferative disorder in a subject in combination with trastuzumab ortrastuzumab and 5-FC.

Alternatively, HER2 and the modifications described above can beexpressed in a separate vector containing a different ENV gene or otherappropriate surface protein. This vector can be replication competent(Logg et al. J. Mol Biol. 369:1214 2007) or non-replicative “firstgeneration” retroviral vector that encodes the envelope and the gene ofinterest (Emi et al. J. Virol 65:1202 1991). In the latter case thepre-existing viral infection will provide complementary gag and pol toallow infective spread of the “non-replicative” vector from anypreviously infected cell. Alternate ENV and glycoproteins includexenotropic and polytropic ENV and glycoproteins capable of infectinghuman cells, for example ENV sequences from the NZB strain of MLV andglycoproteins from MCF, VSV, GALV and other viruses (Palu 2000, Baum etal., Mol. Therapy, 13(6):1050-1063, 2006). For example, a polynucleotidecan comprise a sequence wherein the GAG and POL and yCD2 genes of SEQ IDNO: 19 are deleted, the ENV corresponds to a xenotropic ENV domain ofNZB MLV or VSV-g, and the IRES or a promoter such as RSV is operativelylinked directly to HER2, HER2 ECDTM, HER2 ECDIVTM, or HER2 SECDIVTM.

Mixed infection of cells by VSVG pseudotyped virus and amphotropicretrovirus results in the production of progeny virions bearing thegenome of one virus encapsidated by the envelope proteins of the other.The same is true for other envelopes that pseudotype retroviralparticles. For example, infection by retroviruses derived as aboveresults in production of progeny virions capable of encoding yCD2 andHER2 (or variant) in infected cells. The resulting viruses can be usedto treat a cell proliferative disorder in a subject in combination withtrastuzumab or trastuzumab and 5-FC.

Recently, a gamma retrovirus, XMRV, has been associated with prostatecancer in humans with the virus showing a strong preference forreplication in prostate tissue (R. Schlaberg et al. PNAS 106:16351-16356 2009). The virus appears very similar to xenotropic MLV. Inone embodiment of the disclosure, non-replicative retroviral vectors areprovided which carry both a therapeutic gene (cytosine deaminase,thymidine kinase, other prodrug activating genes, interferons, IL-2,IL-12, other cytokines, p53 other anti-oncogenes, anti-cancer miRNA orthe like) and an envelope gene that is capable of being complemented bythe XMRV gag and gag-pol functions such as an amphotropic envelope, aGALV envelope, a VSVg protein envelope, or other envelopes known tothose skilled in the art. The non-replicative vector polynucleotide isdelivered to the prostate cancer in a patient or animal as a DNA or RNAmolecule using one of: non-viral or physical delivery systems; aheterologous viral delivery system such as an adenoviral vector, or as amanufactured retroviral particle. Once delivered the non-replicativevector will be spread by complementation by XMRV and infection ofneighboring cells will take place until the boundary of XMRV infectionis reached, when the XMRV complementation will not be available. Thetherapeutic gene can then have its effect (e.g. after a prodrug isadministered) in the XMRV infected area only. The same rescue effect canbe achieved using a replicative retroviral vector of the disclosure.This strategy (complementary non-replicative vector with a therapeuticgene) can be used with any retroviral disease (HIV infection, HTLV1infection, other cancer associated retroviruses), or with any viral orviral associated disease (HPV infection and HPV E6 & E7 expression incervical cancers, EBV associated lymphomas or carcinomas etc.).

Another aspect of the development of resistance to trastuzumab relatesto the interference with intracellular signaling required for theactivity of trastuzumab. Resistant cells show loss of PTEN and lowerexpression of p27kip1 [Fujita, Brit J. Cancer, 94:247, 2006; Lu et al.,Journal of the National Cancer Institute, 93(24): 1852-1857, 2001; Kuteet al., Cytometry Part A 57A:86-93, 2004). For example, a polynucleotideencoding PTEN (SEQ ID NO:25) can be recombinantly generated orchemically synthesized (BioBasic Inc., Markham, Canada) and operablyinserted directly after the yCD2 polynucleotide in the vector pAC3-yCD2SEQ ID NO: 19 or 22, or with a linker sequence as previously described,or as a replacement for yCD2. In a further example, the PTEN encodingpolynucleotide can be synthesized as above and inserted between the IRESand yCD2 sequences or with a linker as previously described.

Alternatively, PTEN can be expressed in a separate vector containing adifferent ENV gene or other appropriate surface protein. This vector canbe replication competent (Logg et al. J. Mol Biol. 369:1214 2007) ornon-replicative “first generation” retroviral vector that encodes theenvelope and the gene of interest (Emi et al., J. Virol 65:1202 1991).In the latter case the pre-existing viral infection will providecomplementary gag and pol to allow infective spread of the“non-replicative” vector from any previously infected cell. AlternateENV and glycoproteins include xenotropic and polytropic ENV andglycoproteins capable of infecting human cells, for example ENVsequences from the NZB strain of MLV and glycoproteins from MCF, VSV,GALV and other viruses (Palu, Rev Med Virol. 2000, Baum, Mol. Ther.13(6):1050-1063, 2006). For example, a polynucleotide can comprise asequence wherein the GAG and POL and yCD2 genes of SEQ ID NO: 19 aredeleted, the ENV corresponds to a xenotropic ENV domain of NZB MLV orVSV-g, and the IRES or a promoter such as RSV is operatively linkeddirectly to PTEN.

Mixed infection of cells by VSVG pseudotyped virus and amphotropicretrovirus results in the production of progeny virions bearing thegenome of one virus encapsidated by the envelope proteins of the other[Emi 1991]. The same is true for other envelopes that pseudotyperetroviral particles. For example, infection by retroviruses derived asabove results in production of progeny virions capable of encoding yCD2and PTEN (or variant) or PTEN alone in infected cells. The resultingviruses can be used to treat a cell proliferative disorder in a subjectin combination with trastuzumab or trastuzumab and 5-FC.

Similarly, a polynucleotide encoding p27kip1 (SEQ ID NO:27 and 28) canbe chemically synthesized (BioBasic Inc., Markham, Canada) and operablyinserted directly after the yCD2 gene in the vector pAC3-yCD2 SEQ ID NO:19 or with a linker sequence. In a further example, the p27kip1 encodingpolynucleotide can be synthesized as above and inserted between the IRESand yCD2 sequences or with a linker as previously described or in placeof the yCD2 gene.

Alternatively, p27kip1 can be expressed in a separate vector containinga different ENV gene or other appropriate surface protein. This vectorcan be replication competent (C R. Logg et al. J. Mol Biol. 369:12142007) or non-replicative “first generation” retroviral vector thatencodes the envelope and the gene of interest (Emi et al. J. Virol65:1202 1991). In the latter case the pre-existing viral infection willprovide complementary gag and pol to allow infective spread of the“non-replicative” vector from any previously infected cell. AlternateENV and glycoproteins include xenotropic and polytropic ENV andglycoproteins capable of infecting human cells, for example ENVsequences from the NZB strain of MLV and glycoproteins from MCF, VSV,GALV and other viruses (Palu 2000, Baum 2006, supra). For example, apolynucleotide can comprise a sequence wherein the GAG and POL and yCD2genes of SEQ ID NO: 19 are deleted, the ENV corresponds to a xenotropicENV domain of NZB MLV or VSV-g, and the IRES or a promoter such as RSVis operatively linked directly to p27kip1.

Mixed infection of cells by VSVG pseudotyped virus and amphotropicretrovirus results in the production of progeny virions bearing thegenome of one virus encapsidated by the envelope proteins of the other[Emi 1991]. The same is true for other envelopes that pseudotyperetroviral particles. For example, infection by retroviruses derived asabove from both SEQ ID NO: 19 and 22 results in production of progenyvirions capable of encoding yCD2 and p27kip1 (or variant) in infectedcells. The resulting viruses can be used to treat a cell proliferativedisorder in a subject in combination with trastuzumab or trastuzumab and5-FC.

In another example, CD20 is the target for binding of the drug rituximab(Rituxan™, Genentech). Rituximab is a mediator of complement-dependentcytotoxicity (CDC) and ADCC. Cells with higher mean fluorescenceintensity by flow cytometry show enhanced sensitivity to rituximab (vanMeerten et al., Clin Cancer Res 2006; 12(13):4027-4035, 2006).Enhancement of expression of CD20 by introduction of vector expressingCD20 in CD20 low B cells may facilitate optimal triggering of ADCC.

For example, a polynucleotide encoding CD20 (SEQ ID NO:29 and 30) can bechemically synthesized (BioBasic Inc., Markham, Canada) and operablyinserted directly after the yCD2 gene in the vector pAC3-yCD2(-2) SEQ IDNO: 19 or 22 with a linker sequence as previously described, or as areplacement for the yCD2 gene. In a further example, the CD20 encodingpolynucleotide can be synthesized as above and inserted between the IRESand yCD2 sequences or with a linker as previously described. As afurther alternative the CD20 sequence can be inserted into the pAC3-yCD2vector after excision of the CD gene by Psi1 and Not1 digestion.

In still a further example, a polynucleotide encoding CD20 (SEQ ID NO:29and 30) can be chemically synthesized (BioBasic Inc., Markham, Canada)and inserted into a vector containing a non amphotropic ENV gene orother appropriate surface protein (Tedder et al., PNAS, 85:208-212,1988). Alternate ENV and glycoproteins include xenotropic and polytropicENV and glycoproteins capable of infecting human cells, for example ENVsequences from the NZB strain of MLV and glycoproteins from MCF, VSV,GALV and other viruses [Palu 2000, Baum 2006]. For example, apolynucleotide can comprise a sequence wherein the GAG and POL and yCD2genes of SEQ ID NO: 19 are deleted, the ENV corresponds to a xenotropicENV domain of NZB MLV or VSV-g, and the IRES or a promoter such as RSVis operatively linked directly to CD20.

Mixed infection of cells by VSVG pseudotyped virus and amphotropicretrovirus results in the production of progeny virions bearing thegenome of one virus encapsidated by the envelope proteins of the other[Emi 1991]. The same is true for other envelopes that pseudotyperetroviral particles. For example, infection by retroviruses derived asabove from both SEQ ID NO: 19 or 22 results in production of progenyvirions capable of encoding yCD2 and CD20 in infected cells. Theresulting viruses can be used to treat a cell proliferative disorder ina subject in combination with Rituxan and/or 5-FC. Similarly, infectionof a tumor with a vector encoding only the CD20 marker can make thetumor treatable by the use of Rituxan.

Levels of the enzymes and cofactors involved in pyrimidine anabolism canbe limiting. OPRT, thymidine kinase (TK), Uridine monophosphate kinase,and pyrimidine nucleoside phosphorylase expression is low in 5-FUresistant cancer cells compared to sensitive lines (Wang et al., CancerRes., 64:8167-8176, 2004). Large population analyses show correlation ofenzyme levels with disease outcome (Fukui et al., Int'l. J. OF Mol.Med., 22:709-716, 2008). Coexpression of CD and other pyrimidineanabolism enzymes (PAE) can be exploited to increase the activity andtherefore therapeutic index of fluoropyrimidine drugs.

To further increase the genetic stability (see, e.g., FIG. 5) ofyCD2/PAE containing vectors, the enzyme encoding gene can be chemicallysynthesized with random mutations throughout the sequence. Thesemutations can be essentially random or can consist of only mutations atthe wobble position for each amino acids. The library of mutatedsequences is inserted downstream or in place of the yCD2 gene as waspreviously described for SEQ ID NO: 11 and 13 to create a library ofplasmids that can then be used to generate a library of infectiousparticles by transient transfection of 293T cells or equivalent.Sensitive cells can be infected with retrovirus encoding the fusionpolypeptide and subjected to selection with appropriate chemicals.

DNA shuffling or “molecular breeding” allows genetic information to beshuffled, leading to recombinants with desired properties. Differentproteins and enzymes have been improved using DNA shuffling (Stemmer1994 Proc Natl Acad Sci USA 91(22): 10747-51; Stemmer 1994 Nature 370(6488):389-91). Genetic recombination is a major force driving theevolution of many viruses. In retrovirus, recombination between twoco-packaged retroviral genomes may occur at rates as high as 40% perreplication cycle. High rates of recombination at each replication cycleenables genetic information to be shuffled rapidly, leading torecombinants with new pattern of mutations and phenotypes within a shortperiod of time. For example, molecular breeding of retrovirus containinga library of recombinant ecotropic envelope sequences from six murineleukemia virus resulted in a viral clone with a new tropism. Using thesame method, several viral clones were selected with improved stabilityand processing yields (Soong et al., 2000 Nat Genet 25(4):436-9; Powellet al., 2000 Nat Biotechnol 18(12):1279-82). In order to generatevectors that can replicate in cells that are resistant to retroviralinfection because of viral restriction or inhibitory factors, such asAPOBEC, Trim5alpha, tetherin, Zap or other elements in cells that renderthem resistant to retroviral infection (D. Wolf & SP. Goff, Annu. Rev.Genet. 2008. 42:143-63) the vectors of the disclosure can be used toexpress libraries of random peptide libraries normally expressed inyeast libraries (F. Hoppe-Seyler & K. Butz J Mo Med 78:426-430 (2000);R. Wolkowicz et al. J. Biol. Chem. 280:15195-15201 (2005); bothincorporated by reference), made from inserts of random nucleotidesyntheses into the vectors. These inserts can be expressed asstand-alone peptides expressed from the IRES or otherwise, or can betagged at the beginning, in the middle of, or at the end of the proteinthat it is desired to express. For example it is known that yeastcytosine deaminase tolerates fusion to the C terminus of a protein (KN.Barton et al. Mol Ther 13:347-356 2006). Alternatively the peptides canbe inserted at the beginning, middle or end of viral structural proteinsin the same way. Not all insertion sites will be well tolerated butvarious useful sites are known. The peptides can be from 6 to 60 aminoacids in length, typically between 8 and 20 amino acids. Peptides thatbind to and inactivate known antiviral agents may be select byconventional yeast two hybrid methods but this is laborious and has nofunctional guarantee of success. However, if the virus itself isexpressing the peptide library by bulk insertion of library nucleotidesequences into the vector as a DNA plasmid followed by transienttransfection on 293T cells or equivalent to generate a library ofinfectious particles, then the vector that grows best in the target cellor tumor type is selected by serial growth in that cell type or tumorexplants. Serial passage in the target cell type rapidly select forviruses that carry an inhibitor peptide for any factor that inhibitsviral replication in that cell type. In order to maintain a gooddiversity of peptides, and supply an opportunity for mutations to occur,if necessary, the target cell is grown mixed with a cell type thatsupports viral replication well (e.g. HT1080 human fibrosarcoma) toprovide further copies of the library of viruses and to let the errorprone reverse transcriptase introduce occasional random mutations, thatmay be advantageous.

The virus coming from the cells is monitored on each passage for itsdiversity, by direct sequencing of the insert or otherwise, and may berecycled through the selection procedure several times. The selectedviruses are cloned out from the viral supernatant or the cells by PCRacross the insert, insertion in a plasmid and sequencing of individualplasmid clones. The identified peptide aptamers are then rechecked fortheir ability to confer replication advantage in a particular cell typesuch as a particular tumor type or particular blood cell types etc. Thepeptide aptamers are also used directly to identify the cellular elementwith which it interacts by methods known to those in the art.

The peptide aptamer sequence is then incorporated as before in a viralvector that has the desired replication capacity, and carries atherapeutic gene as described elsewhere in the disclosure. Such a vectoris used for therapeutic purposes as described in this disclosure.

Polynucleotide sequence incorporated into vectors are sometimes unstableresulting in deletion of the polynucleotide sequence from the viralgenome over time. The basis for this is not well understood, but it isbelieved to be sequence dependent Molecular breeding using the vectorsdescribed herein to select for recombinant viral clones that haveacquired optimal recombinations within the heterologous polynucleotidesequence is employed to select for viral clones that have greater vectorstability.

For example, the HSV-TK coding sequence is not as stable as desired insome situations. Molecular breeding of recombinant retroviral vectorsencompass a pool of degenerated coding sequence of HSV-TK is performedto select recombinant vectors that have great vector stability. Randomlymutagenized Herpes Thymidine Kinase (TK) is chemically synthesized (BioBasic Inc., Markham, Canada). The synthetic sequence is inserted 3′ ofthe yCD2 sequence in SEQ ID NO:19, or by itself in the pAC3-yCD2 vectorback bones after excision of the CD2 gene. The retroviral vector mixtureis packaged as described elsewhere herein. Mouse fibroblast LMTK− cellsor humans 143Tk− are infected with vector and selected for TK activityin HAT media (Hiller et al., Mol. Cell Biol. 8(8):3298-3302, 1988).Serial passage of supernatants of resistant cells to fresh LMTK−/143Tk−cells again selected in HAT media results in selection of stable vectorsexpressing TK. TK+ resistant cells can be isolated and TK sequencesrescued by standard PCR based techniques for mutation analysis (Cowellet al., CDNA Library Protocols, Published by Humana Press, 1996). Inthis manner, sequences are selected for both expression of functionalprotein and genomic stability of retroviral vector construct. Similarstrategies can be employed for UPRT (SEQ ID NO: 11, 13), OPRT (SEQ IDNO: 15, 17) and other genes of interest. In addition, the serial passagestrategy can be used for non-selectable genes and the genomic DNA afterserial passage screened for full length inserts by PCR across theIRES-insert gene (see FIG. 5). The full length inserts can be purifiedand cloned out back into the viral vector then retested. Several cyclesof this procedure can be performed to select the most stable gene. Thisstrategy can also be used for passage in animals with or without tumors,and even in patient tissue.

Alternatively, OPRT, UPRT, TK or other PAE can be expressed in aseparate vector containing a different env gene or other appropriatesurface glycoprotein. This vector can be replication competent (Logg etal. J. Mol Biol. 369:1214 2007) or non-replicative “first generation”retroviral vector that encodes the envelope and the gene of interest(Emi et al. J. Virol 65:1202 1991). In the latter case the pre-existingviral infection will provide complementary gag and pol to allowinfective spread of the “non-replicative” vector from any previouslyinfected cell. Alternate ENV and glycoproteins include xenotropic andpolytropic ENV and glycoproteins capable of infecting human cells, forexample ENV sequences from the NZB strain of MLV and glycoproteins fromMCF, VSV, GALV and other viruses [Palu 2000, Baum 2006, supra]. Forexample, a polynucleotide can comprise a sequence wherein the GAG andPOL genes are deleted, the ENV corresponds to a xenotropic ENV domainfrom NZB MLV or VSV-g, and the IRES or a promoter such as RSV isoperatively linked directly to OPRT, UPRT, TK, or other PAE gene.

Mixed infection of cells by VSV-g pseudotyped virus and amphotropicretrovirus results in the production of progeny virions bearing thegenome of one virus encapsidated by the envelope proteins of the other(Emi et al., J. Virol. 65:1202, 1991). The same is true for otherenvelopes that pseudotype retroviral particles. For example, infectionby retroviruses derived as above from both SEQ ID NO: 19 and 22 resultsin production of progeny virions capable of encoding yCD2 and OPRT ininfected cells. The resulting viruses can be used to treat a cellproliferative disorder in a subject in combination with 5-FC.

The recombinant retrovirus of the disclosure can be used for thetreatment of a neuronal disorder for example, may optionally contain anexogenous gene, for example, a gene which encodes a receptor or a genewhich encodes a ligand. Such receptors include receptors which respondto dopamine, GABA, adrenaline, noradrenaline, serotonin, glutamate,acetylcholine and other neuropeptides, as described above. Examples ofligands which may provide a therapeutic effect in a neuronal disorderinclude dopamine, adrenaline, noradrenaline, acetylcholine,gamma-aminobutyric acid and serotonin. The diffusion and uptake of arequired ligand after secretion by an infected donor cell would bebeneficial in a disorder where the subject's neural cell is defective inthe production of such a gene product. A cell genetically modified tosecrete a neurotrophic factor, such as nerve growth factor, (NGF), mightbe used to prevent degeneration of cholinergic neurons that mightotherwise die without treatment.

Alternatively, cells being grafted into a subject with a disorder of thebasal ganglia, such as Parkinson's disease, can be modified to containan exogenous gene encoding L-DOPA, the precursor to dopamine.Parkinson's disease is characterized by a loss of dopamine neurons inthe substantia-nigra of the midbrain, which have the basal ganglia astheir major target organ.

Other neuronal disorders that can be treated similarly by the method ofthe disclosure include Alzheimer's disease, Huntington's disease,neuronal damage due to stroke, and damage in the spinal cord.Alzheimer's disease is characterized by degeneration of the cholinergicneurons of the basal forebrain. The neurotransmitter for these neuronsis acetylcholine, which is necessary for their survival. Engraftment ofcholinergic cells infected with a recombinant retrovirus of thedisclosure containing an exogenous gene for a factor which would promotesurvival of these neurons can be accomplished by the method of thedisclosure, as described. Following a stroke, there is selective loss ofcells in the CA1 of the hippocampus as well as cortical cell loss whichmay underlie cognitive function and memory loss in these patients. Onceidentified, molecules responsible for CA1 cell death can be inhibited bythe methods of this disclosure. For example, antisense sequences, or agene encoding an antagonist can be transferred to a neuronal cell andimplanted into the hippocampal region of the brain.

For diseases due to deficiency of a protein product, gene transfer couldintroduce a normal gene into the affected tissues for replacementtherapy, as well as to create animal models for the disease usingantisense mutations. For example, it may be desirable to insert a FactorIX encoding nucleic acid into a retrovirus for infection of a muscle orliver cell.

The disclosure also provides gene therapy for the treatment of cellproliferative or immunologic disorders. Such therapy would achieve itstherapeutic effect by introduction of an antisense or dominant negativeencoding polynucleotide into cells having the proliferative disorder,wherein the polynucleotide binds to and prevents translation orexpression of a gene associated with a cell-proliferative disorder.Delivery of heterologous nucleic acids useful in treating or modulatinga cell proliferative disorder (e.g., antisense polynucleotides) can beachieved using a recombinant retroviral vector of the disclosure. Inanother embodiment, a cell proliferative disorder is treated byintroducing a CD polynucleotide of the disclosure, expressing thepolynucleotide to produce a polypeptide comprising cytosine deaminaseactivity and contacting the cell with 5-fluorocytosine in an amount andfor a period of time to produce a cytotoxic amount of 5-FU.

A number of chemotherapeutic agents are currently on the market havingvarying degrees of success from full remission to temporary remissionand prolonged life with expected recurrence. Some of the cancertherapeutic agents on the market target the vascular angiogenicproperties of tumor. The composition target the angiogenesis of tumorsseeking to reduces blood supply and nutrients to the tumor or cancer andthereby reduce the tumor and prolong a subject's life. VEGF is anangiogenic factor known to play a role in tumor growth. Thus,antagonists of VEGF have been developed as anti-cancer agents.

Human VEGF mediates neoangiogenesis in normal and malignant vasculature;it is overexpressed in most malignancies and high levels have correlatedwith a greater risk of metastases and poor prognosis in many. When VEGFinteracts with its receptor in in vitro models of angiogenesis,endothelial cell proliferation and new blood vessel formation occur. Inanimal models, VEGF has been demonstrated to induce vascularendothelial-cell proliferation/migration, sustain survival ofnewly-formed blood vessels, and enhance vascular permeability.

A VEGF antagonist agent is one that targets or negatively regulates theVEGF signaling pathway. Examples include VEGF inhibitors (e.g., agentsthat directly inhibit VEGF (e.g., VEGF-A, -B, -C, or -D), such as bybinding VEGF (e.g., anti-VEGF antibodies such as bevacizumab (AVASTIN®)or ranibizumab (LUCENTIS®), or other inhibitors such as pegaptanib,NEOVASTAT®, AE-941, VEGF Trap, and PI-88)), modulators of VEGFexpression (e.g., INGN-241, oral tetrathiomolybdate, 2-methoxyestradiol,2-methoxyestradiol nanocrystal dispersion, bevasiranib sodium, PTC-299,Veglin), inhibitors of a VEGF receptor (e.g., KDR or VEGF receptor III(Flt4), for example anti-KDR antibodies, VEGFR2 antibodies such asCDP-791, IMC-1121B, VEGFR2 blockers such as CT-322), modulators of VEGFRexpression (e.g., VEGFR1 expression modulator Sirna-027) or inhibitorsof VEGF receptor downstream signaling. In some aspects described herein,the VEGF antagonist agent is bevacizumab, pegaptanib, ranibizumab,sorafenib, sunitinib, AE-941, VEGF Trap, pazopanib, vandetanib,vatalanib, cediranib, fenretinide, squalamine, INGN-241, oraltetrathiomolybdate, tetrathiomolybdate, Panzem NCD, 2-methoxyestradiol,AEE-788, AG-013958, bevasiranib sodium, AMG-706, axitinib, BIBF-1120,CDP-791, CP-547632, PI-88, SU-14813, SU-6668, XL-647, XL-999, IMC-1121B,ABT-869, BAY-57-9352, BAY-73-4506, BMS-582664, CEP-7055, CHIR-265,CT-322, CX-3542, E-7080, ENMD-1198, OSI-930, PTC-299, Sirna-027,TKI-258, Veglin, XL-184, or ZK-304709.

Bevacizumab (AVASTATIN®) (rhuMAb-VEGF) (Anti-VEGF monoclonal antibody)is a recombinant human/murine chimeric monoclonal antibody directedagainst vascular endothelial growth factor (VEGF)). It is prepared byengineering VEGF-binding residues of a murine anti-VEGF monoclonalantibody into framework regions of human immunoglobulin-1 (IgG1) (ProdInfo Avastin, 2004). Only 7% of the amino acid sequence is derived fromthe murine antibody, with 93% from IgG1. Bevacizumab binds andneutralizes all human VEGF forms via recognition of binding sites forthe two human VEGF receptor types (flt-1 and flk-1). In animal models,the antibody has been shown to stabilize established tumors or suppresstumor growth by inhibiting angiogenesis induced by VEGF.

The pharmacokinetics of bevacizumab are linear after doses of 0.3 mg/kgor greater (Anon, 2002). Following 90-minute intravenous infusions of0.3, 1, 3, and 10 mg/kg in advanced cancer patients (n=25), peak serumconcentrations of bevacizumab ranged from 5 to 9 mcg/mL, 21 to 39mcg/mL, 52 to 92 mcg/mL, and 186 to 294 mcg/mL, respectively; slightaccumulation was observed with repeat doses (weekly), but this was notsignificant and pharmacokinetics remained linear. Steady-state levels ofbevacizumab were obtained in 100 days after 1 to 20 mg/kg weekly, every2 weeks, or every 3 week.

The recommended dose of bevacizumab is 5 milligrams/kilogram infusedintravenously over 30 minutes every 2 weeks until disease progressiondiminishes. Bevacizumab should follow chemotherapy. Efficacy ofsingle-agent bevacizumab has not been established. Bevacizumab (whichmay be co-administered with the gemcitabine and docetaxel, or within aweek before or after chemotherapy), is administered intravenously, atabout 1 mg/kg to about 15 mg/kg, preferably about 5 mg/kg.

The methods and compositions of the disclosure are useful in combinationtherapies including therapies with bevacizumab. As described herein areplication competent retrovirus (RCR) of the disclosure comprising atherapeutic (e.g., a cytotoxic gene) is useful in treating cellproliferative disorders. An advantage of the RCR of the disclosureincludes its ability to infect replicating cells cancer cells. Where thetransgene of the vector comprises a cytotoxic gene (e.g., a gene thatencodes a polypeptide that converts a non-cytotoxic agent to a cytotoxicagent) provides the ability to kill cancer cells.

The disclosure provides methods for treating cell proliferativedisorders such as cancer and neoplasms comprising administering an RCRvector of the disclosure followed by treatment with a chemotherapeuticagent or anti-cancer agent. In one aspect, the RCR vector isadministered to a subject for a period of time prior to administrationof the chemotherapeutic or anti-cancer agent that allows the RCR toinfect and replicate. The subject is then treated with achemotherapeutic agent or anti-cancer agent for a period of time anddosage to reduce proliferation or kill the cancer cells. In one aspect,if the treatment with the chemotherapeutic or anti-cancer agent reduces,but does not kill the cancer/tumor (e.g., partial remission or temporaryremission), the subject may then be treated with a non-toxic therapeuticagent (e.g., 5-FC) that is converted to a toxic therapeutic agent incells expression a cytotoxic gene (e.g., cytosine deaminase) from theRCR.

Using such methods the RCXR vectors of the disclosure are spread duringa replication process of the tumor cells, such cells can then be killedby treatment with an anti-cancer or chemotherapeutic agent and furtherkilling can occur using the RCR treatment process described herein.

In yet another embodiment of the disclosure, the heterologous gene cancomprise a coding sequence for a target antigen (e.g., a cancerantigen). In this embodiment, cells comprising a cell proliferativedisorder are infected with an RCR comprising a heterologouspolynucleotide encoding the target antigen to provide expression of thetarget antigen (e.g., overexpression of a cancer antigen). An anticanceragent comprising a targeting cognate moiety that specifically interactswith the target antigen is then administered to the subject. Thetargeting cognate moiety can be operably linked to a cytotoxic agent orcan itself be an anticancer agent. Thus, a cancer cell infected by theRCR comprising the targeting antigen coding sequences increases theexpression of target on the cancer cell resulting in increasedefficiency/efficacy of cytotoxic targeting.

Blocking of interactions between cells of the immune system has beenshown to have significant immunological effects, either activating orsuppressing (Waldmann Annu Rev Med. 57:65 2006). For example, blockadeof the interaction of CTLA-4 (CD 152) and B7.1 (CD80) which modulatesthe activation of T cells has been shown to cause immune stimulation,presumably by blocking this suppressive interaction (Peggs et al. Curr.Opin. Immunol. 18:206, 2006). This blockade can potentially be achievedeither by antibodies against CTLA-4 or by soluble B7.1. Systemicadministration of these types of molecules can have undesirable globaleffects which can at a minimum lead to deleterious side-effects or evendeath in the case of one CD28 agonist (Suntharalingam et al. NEJM 3551018 2006). Pfizer has been developing one such anti-CTLA-4 blockadingantibody (CP-675,206) as an anticancer reagent but has recently stoppeddevelopment because of significant side effects. Local delivery ofblockading molecules that are released into the local environment, fromthe tumor after infection with a replication competent vector encodingsuch molecules that are released into the extracellular space, providesthe immune modulation locally and can avoid these serious side effects.The blockading molecules are antibodies, single chain antibodies,soluble versions of the natural ligand or other peptides that bind suchreceptors.

In yet another embodiment, an RCR of the disclosure can comprise acoding sequence comprising a binding domain (e.g., an antibody, antibodyfragment, antibody domain or receptor ligand) that specificallyinteracts with a cognate antigen or ligand. The RCR comprising thecoding sequence for the binding domain can then be used to infect cellsin a subject comprising a cell proliferative disorder such as a cancercell or neoplastic cell. The infected cell will then express the bindingdomain or antibody. An antigen or cognate operably linked to a cytotoxicagent or which is cytotoxic itself can then be administered to asubject. The cytotoxic cognate will then selectively kill infected cellsexpressing the binding domain. Alternatively the binding domain itselfcan be an anti-cancer agent.

As used herein, the term “antibody” refers to a protein that includes atleast one immunoglobulin variable domain or immunoglobulin variabledomain sequence. For example, an antibody can include a heavy (H) chainvariable region (abbreviated herein as VH), and a light (L) chainvariable region (abbreviated herein as VL). In another example, anantibody includes two heavy (H) chain variable regions and two light (L)chain variable regions. The term “antibody” encompasses antigen-bindingfragments of antibodies (e.g., single chain antibodies, Fab fragments,F(ab′)₂, a Fd fragment, a Fv fragments, and dAb fragments) as well ascomplete antibodies.

The VH and VL regions can be further subdivided into regions ofhypervariability, termed “complementarity determining regions” (CDR),interspersed with regions that are more conserved, termed “frameworkregions” (FR). The extent of the framework region and CDRs has beenprecisely defined (see, Kabat, E. A., et al. (1991) Sequences ofProteins of Immunological Interest, Fifth Edition, U.S. Department ofHealth and Human Services, NIH Publication No. 91-3242, and Chothia, C.et al. (1987) J. Mol. Biol. 196:901-917). Kabat definitions are usedherein. Each VH and VL is typically composed of three CDRs and four FRs,arranged from amino-terminus to carboxy-terminus in the following order:FR1, CDR1, FR2, CDR2, FR3, CDR3, FR4.

An “immunoglobulin domain” refers to a domain from the variable orconstant domain of immunoglobulin molecules. Immunoglobulin domainstypically contain two .beta.-sheets formed of about seven.beta.-strands, and a conserved disulphide bond (see, e.g., A. F.Williams and A. N. Barclay 1988 Ann. Rev Immunol. 6:381-405). Thecanonical structures of hypervariable loops of an immunoglobulinvariable can be inferred from its sequence, as described in Chothia etal. (1992) J. Mol. Biol. 227:799-817; Tomlinson et al. (1992) J. Mol.Biol. 227:776-798); and Tomlinson et al. (1995) EMBO J. 14(18):4628-38.

As used herein, an “immunoglobulin variable domain sequence” refers toan amino acid sequence which can form the structure of an immunoglobulinvariable domain. For example, the sequence may include all or part ofthe amino acid sequence of a naturally-occurring variable domain. Forexample, the sequence may omit one, two or more N- or C-terminal aminoacids, internal amino acids, may include one or more insertions oradditional terminal amino acids, or may include other alterations. Inone embodiment, a polypeptide that includes immunoglobulin variabledomain sequence can associate with another immunoglobulin variabledomain sequence to form a target binding structure (or “antigen bindingsite”), e.g., a structure that interacts with Tiel, e.g., binds to orinhibits Tiel.

The VH or VL chain of the antibody can further include all or part of aheavy or light chain constant region, to thereby form a heavy or lightimmunoglobulin chain, respectively. In one embodiment, the antibody is atetramer of two heavy immunoglobulin chains and two light immunoglobulinchains, wherein the heavy and light immunoglobulin chains areinter-connected by, e.g., disulfide bonds. The heavy chain constantregion includes three domains, CH1, CH2 and CH3. The light chainconstant region includes a CL domain. The variable region of the heavyand light chains contains a binding domain that interacts with anantigen. The constant regions of the antibodies typically mediate thebinding of the antibody to host tissues or factors, including variouscells of the immune system (e.g., effector cells) and the firstcomponent (Clq) of the classical complement system. The term “antibody”includes intact immunoglobulins of types IgA, IgG, IgE, IgD, IgM (aswell as subtypes thereof). The light chains of the immunoglobulin may beof types kappa or lambda. In one embodiment, the antibody isglycosylated. An antibody can be functional for antibody-dependentcytotoxicity and/or complement-mediated cytotoxicity.

The term “monospecific antibody” refers to an antibody that displays asingle binding specificity and affinity for a particular target, e.g.,epitope. This term includes a “monoclonal antibody” which refers to anantibody that is produced as a single molecular species, e.g., from apopulation of homogenous isolated cells. A “monoclonal antibodycomposition” refers to a preparation of antibodies or fragments thereofof in a composition that includes a single molecular species ofantibody. In one embodiment, a monoclonal antibody is produced by amammalian cell. One or more monoclonal antibody species may be combined.

One or more regions of an antibody can be human or effectively human.For example, one or more of the variable regions can be human oreffectively human. For example, one or more of the CDRs can be human,e.g., HC CDR1, HC CDR2, HC CDR3, LC CDR1, LC CDR2, and LC CDR3. Each ofthe light chain CDRs can be human. HC CDR3 can be human. One or more ofthe framework regions can be human, e.g., FR1, FR2, FR3, and FR4 of theHC or LC. In one embodiment, all the framework regions are human, e.g.,derived from a human somatic cell, e.g., a hematopoietic cell thatproduces immunoglobulins or a non-hematopoietic cell. In one embodiment,the human sequences are germline sequences, e.g., encoded by a germlinenucleic acid. One or more of the constant regions can be human oreffectively human. In another embodiment, at least 70, 75, 80, 85, 90,92, 95, or 98% of the framework regions (e.g., FR1, FR2, and FR3,collectively, or FR1, FR2, FR3, and FR4, collectively) or the entireantibody can be human or effectively human. For example, FR1, FR2, andFR3 collectively can be at least 70, 75, 80, 85, 90, 92, 95, 98, or 99%identical to a human sequence encoded by a human germline V segment of alocus encoding a light or heavy chain sequence.

All or part of an antibody can be encoded by an immunoglobulin gene or asegment thereof. Exemplary human immunoglobulin genes include the kappa,lambda, alpha (IgA1 and IgA2), gamma (IgG1, IgG2, IgG3, IgG4), delta,epsilon and mu constant region genes, as well as the myriadimmunoglobulin variable region genes. Full-length immunoglobulin lightchains (about 25 Kd or 214 amino acids) are encoded by a variable regiongene at the NH2-terminus (about 110 amino acids) and a kappa or lambdaconstant region gene at the COOH— terminus. Full-length immunoglobulinheavy chains (about 50 Kd or 446 amino acids), are similarly encoded bya variable region gene (about 116 amino acids) and one of the otheraforementioned constant region genes, e.g., gamma (encoding about 330amino acids). A light chain refers to any polypeptide that includes alight chain variable domain. A heavy chain refers to any polypeptidethat a heavy chain variable domain.

The term “antigen-binding fragment” of a full-length antibody (or simply“antibody portion,” or “fragment”), as used herein, refers to one ormore fragments of a full-length antibody that retain the ability tospecifically bind to a target of interest. Examples of binding fragmentsencompassed within the term “antigen-binding fragment” of a full lengthantibody include (i) a Fab fragment, a monovalent fragment consisting ofthe VL, VH, CL and CH1 domains; (ii) a F(ab′).sub.2 fragment, a bivalentfragment including two Fab fragments linked by a disulfide bridge at thehinge region; (iii) a Fd fragment consisting of the VH and CH1 domains;(iv) a Fv fragment consisting of the VL and VH domains of a single armof an antibody, (v) a dAb fragment (Ward et al., (1989) Nature341:544-546), which consists of a VH domain; and (vi) an isolatedcomplementarity determining region (CDR) that retains functionality.Furthermore, although the two domains of the Fv fragment, VL and VH, arecoded for by separate genes, they can be joined, using recombinantmethods, by a synthetic linker that enables them to be made as a singleprotein chain in which the VL and VH regions pair to form monovalentmolecules known as single chain Fv (scFv). See e.g., Bird et al. (1988)Science 242:423-426; and Huston et al. (1988) Proc. Natl. Acad. Sci. USA85:5879-5883.

Antibody fragments can be obtained using any appropriate techniqueincluding conventional techniques known to those with skill in the art.The term “monospecific antibody” refers to an antibody that displays asingle binding specificity and affinity for a particular target, e.g.,epitope. This term includes a “monoclonal antibody” or “monoclonalantibody composition,” which as used herein refer to a preparation ofantibodies or fragments thereof of single molecular composition. As usedherein, “isotype” refers to the antibody class (e.g., IgM or IgG1) thatis encoded by heavy chain constant region genes.

The disclosure provides a method of treating a subject having a cellproliferative disorder. The subject can be any mammal, and is preferablya human. The subject is contacted with a recombinant replicationcompetent retroviral vector of the disclosure. The contacting can be invivo or ex vivo. Methods of administering the retroviral vector of thedisclosure are known in the art and include, for example, systemicadministration, topical administration, intraperitoneal administration,intra-muscular administration, intracranial, cerebrospinal, as well asadministration directly at the site of a tumor or cell-proliferativedisorder. Other routes of administration known in the art.

Thus, the disclosure includes various pharmaceutical compositions usefulfor treating a cell proliferative disorder. The pharmaceuticalcompositions according to the disclosure are prepared by bringing aretroviral vector containing a heterologous polynucleotide sequenceuseful in treating or modulating a cell proliferative disorder accordingto the disclosure into a form suitable for administration to a subjectusing carriers, excipients and additives or auxiliaries. Frequently usedcarriers or auxiliaries include magnesium carbonate, titanium dioxide,lactose, mannitol and other sugars, talc, milk protein, gelatin, starch,vitamins, cellulose and its derivatives, animal and vegetable oils,polyethylene glycols and solvents, such as sterile water, alcohols,glycerol and polyhydric alcohols. Intravenous vehicles include fluid andnutrient replenishers. Preservatives include antimicrobial,anti-oxidants, chelating agents and inert gases. Other pharmaceuticallyacceptable carriers include aqueous solutions, non-toxic excipients,including salts, preservatives, buffers and the like, as described, forinstance, in Remington's Pharmaceutical Sciences, 15th ed. Easton: MackPublishing Co., 1405-1412, 1461-1487 (1975) and The National FormularyXIV., 14th ed. Washington: American Pharmaceutical Association (1975),the contents of which are hereby incorporated by reference. The pH andexact concentration of the various components of the pharmaceuticalcomposition are adjusted according to routine skills in the art. SeeGoodman and Gilman's The Pharmacological Basis for Therapeutics (7thed.).

For example, and not by way of limitation, a retroviral vector useful intreating a cell proliferative disorder will include an amphotropic ENVprotein, GAG, and POL proteins, a promoter sequence in the U3 regionretroviral genome, and all cis-acting sequence necessary forreplication, packaging and integration of the retroviral genome into thetarget cell.

The following Examples are intended to illustrate, but not to limit thedisclosure. While such Examples are typical of those that might be used,other procedures known to those skilled in the art may alternatively beutilized.

EXAMPLES Example 1. Modification of Vector Backbone of pACE-GFPemd topAC3-GFPemd and Insertion of Cytosine Deaminase Gene Sequences in Placeof GFP

The previous back bone of the pACE-GFPemd plasmid (U.S. Pat. No.6,899,871, Wang et al. Hum Gene Ther 14:117 2003) was modified in 3 waysas shown in FIG. 3E. The modifications were made by PCR-mediated,oligonucleotide-directed mutagenesis (Logg et al., J. Mol Biol 369:1214, 2007; see also “Molecular Biology and Biotechnology” Eds. J M.Walker, R. Rapley, Royal Society of Chemistry, London UK, 2000). Thefollowing modifications were made. 1) The nucleic acid sequence at thep15 region at 3′ end of the amphotropic env gene was originally derivedfrom the ecotropic envelope—this sequence was replaced by thecorresponding sequence from the 4070A amphotropic envelope; the encodedenvelope amino acids are identical in the two constructs. 2) The IRESsequence 3′ end was modified to allow easier insertion of transgenes ofchoice with insertion of a PstI1 site and small imperfect repeats ateither end of the IRES transgene site were removed. 3) Residual viralsequence downstream of the 3′LTR was removed. The resultant plasmid ispACE-emdGFP (aka pACE-GFP, pACE-eGFP and T5.0006) was used as a basisfor the vectors encoding cytosine deaminase and variants. Two methods ofinserting the coding sequence cassettes were used initially. The firstmethod resulted in the sequence 5′TTATAAT3′ (SEQ ID NO:73), and thesecond in the sequence 5′TTATAA3′ (SEQ ID NO:74) immediately upstream ofthe ATG start codon. The second method was simpler, as it involvedsimple PstI1 and Not1 enzyme cuts in the vector and the syntheticcytosine deaminase genes, followed by religation. Vectors with cytosinedeaminase inserts were made both ways with the CDopt (CD1) and theCDopt+3pt (CD2) (see FIG. 2) coding sequences and infectious virus prepsmade by transient transfection of 293T cells as described in Example 3.U87 cells were then infected in culture, at an MOI of 0.1, and the cellsgrown until 100% infected. Cell extracts of 100% infected cells wereassayed for cytosine deaminase activity as described in Example 6 andthe specific activity of the enzyme was found to be equivalent forconstructs with either upstream sequence, that were otherwise identical.Therefore in the table in FIG. 2, pACE-eGFP (T5.0006) and pACE-yCD(T5.0007) have the first upstream sequence, while all other constructsthat were further tested have the second. Subsequently vectors withdifferent gene inserts have been routinely constructed withstraightforward PStI1 and Not 1 cuts.

See FIG. 3A below for a diagram of the vector construct for the initialtransfected replication-competent retrovirus. CMV is the human CMVimmediate early promoter, U3, R and U5 are the corresponding regions ofthe viral long terminal repeat (LTR). Gag, pol and env are the viralprotein coding regions. FIGS. 3B and 3D shows the plasmid structure anda sequence of the disclosure.

The vector of the disclosure provides a number of differences comparedto the vector of Tai et al., Mol. Ther. 12:842, 2005. The Tai et al.vector has been altered to eliminate about 70 bp of MLV sequencedownstream from the 3′LTR. The DNA sequence downstream of the ClaI sitein the envelope was changed to an amphotropic envelope sequence. Thischange does not change the amino acid sequence of the envelope. Inaddition, small repeats on either side of the IRES-CD cassette have beeneliminated to avoid instability due to homologous recombination. Thesechanges also unexpectedly provided increased stability of the vectorduring replication and passaging in host cells (FIG. 5).

It is recognized that after reverse transcription and the firstintegration event into treated cells, the DNA provirus and anysubsequent progeny retrovirus has a conventional LTR structure from MLVon either end. This configuration has been shown to be stable aftermultiple cycles of infection (See FIG. 5 below).

Example 2. Genetic Enhancements to the Wild Type Yeast CytosineDeaminase Gene

Two sets of changes have been made: (1) three positional mutations whichchange three amino acids (A23L, I140L and V108I) to increase thermalstability of the yeast cytosine deaminase protein and (2) additionalgene sequence modifications to enhance human codon usage sequences toimprove protein translation efficiency in human cells without furtherchanges to the amino acid sequence.

Sequence design for CD included CD-optimized, CD-UPRT (+/− linker) andCD-OPRTase (+/− linker). The final cytosine deaminase coding sequencecan comprise at the 5′ end a PSI1 site (full length) and 3′ end Not1site plus poly A tail for PSI1/Not1 cassette based strategy. Sequencescassettes were ordered from, and provided by, a commercial vendor(BioBasic Inc., Markham, Ontario, Canada).

The following sequence comprising a yeast cytosine deaminase was usedfor cloning, optimizing and mutation (the boxed nucleic acids comprisethe restriction sites—Psi1 and Not1—used in subsequent methods forcloning:

(SEQ ID NO: 43)

ATGAGGAGGCGGCCTTAGGTTACAAAGAGGGTGGTGTTCCTATTGGCGGATGTCTTATCAATAACAAAGACGGAAGTGTTCTCGGTCGTGGTCACAACATGAGATTTCAAAAGGGATCCGCCACACTACATGGTGAGATCTCCACTTTGGAAAACTGTGGGAGATTAGAGGGCAAAGTGTACAAAGATACCACTTTGTATACGACGCTGTCTCCATGCGACATGTGTACAGGTGCCATCATCATGTATGGTATTCCACGCTGTGTTGTCGGTGAGAACGTTAATTTCAAAAGTAAGGGCGAGAAATATTTACAAACTAGAGGTCACGAGGTTGTTGTTGTTGACGATGAGAGGTGTAAAAAGATCATGAAACAATTTATCGATGAAAGACCTCAGGATTGGTTTGAAG

GG

The following Table summarizes the genes and resulting plasmid vectorsthat were made and their names.

TABLE Vector constructs and names Identity Reference Original 5′LTRTrans- Code name Name Prom Envelope Vector IRES gene 3′LTR T5.0000pACE-yCD pACE-CD CMV Ampho pACE EMCV Wt MLV U3 (Tai et al. (4070A) yeast2005) CD T5.0001 pAC3-yCD1 CDopt CMV Ampho pAC3 EMCV modified MLV U3sequence (4070A) CD T5.0002 pAC3-yCD2 CDopt + 3 pt CMV Ampho pAC3 EMCVModified MLV U3 (4070A) CD T5.0003 pAC3-yCD2-U Cdopt + 3 pt- CMV AmphopAC3 EMCV CD2- MLV U3 UPRT (4070A) UPRT T5.0004 pAC3-yCD2-O CDopt + 3pt- CMV Ampho pAC3 EMCV CD2- MLV U3 OPRT (4070A) OPRT T5.0005pAC3-yCD2-LO CDopt + 3 pt- CMV Ampho pAC3 EMCV CD2-L- MLV U3 LINK-OPRT(4070A) OPRT T5.0006 pAC3-eGFP pAC3-emd, CMV Ampho pAC3 EMCV Emerald MLVU3 pAC3GFP (4070A) GFP T5.0007 pAC3-yCD pAC3-yCD CMV Ampho pAC3 EMCV WtMLV U3 (4070A) yeast CD

The replication competent retroviral vector described by Kasahara et al.pACE-CD (U.S. Pat. No. 6,899,871, the disclosure of which isincorporated herein) was used as a basis for additional modifications. Avector (pAC3-yCD) was modified to express a modified yeast cytosinedeaminase gene as described herein and was used in the contructs. SeeFIG. 3A below for a diagram of the vector construct for the initialtransfected replication-competent retrovirus. CMV is the human CMVimmediate early promoter, U3, R and U5 are the corresponding regions ofthe viral long terminal repeat (LTR). Gag, pol and env are the viralprotein coding regions. FIGS. 3B and 3D shows the plasmid structure anda sequence of the disclosure.

After the genes were synthesized at a contractor (Bio Basic Inc.,Markham, Ontario, Canada) they were inserted into the Psi1-Not1 site ofthe pAC3 vector backbone (FIG. 3). The plasmid backbone was normallygenerated by cutting the plasmid pAC3-eGFP with Psi1 and Not1 andpurifying the large (about 11 kb) fragment encoding the plasmid andretroviral backbone).

A. Humanized Codon Optimized CD Gene (CDopt, Aka CD1, T5.0001).

A comparison of a human codon optimized cytosine deaminase of Conrad etal. and PCT WO 99/60008 indicates 91 total codons optimized in both, 36codons identical, 47 codons had third base pair changes (all encode sameamino acid) and 9 codons were different (however they encoded same aminoacid). Of the 9 codons that differed:

AGC (Ser) to TCC (Ser) CGT (Arg) to AGG (Arg) CCA (Pro) to CCT (Pro)

All have equivalent GC content and encode the same amino acid. Thenative yeast gene sequence above was separately codon optimized to givethe following CD gene (CD1) and was called T5.0001 when inserted intothe plasmid vector pAC3 which encodes the replication competentretrovirus (RCR) with IRES.

(SEQ ID NO: 44)

GGCCGCCCTGGGCTACAAGGAGGGCGGCGTGCCTATCGGCGGCTGTCTGATCAACAACAAGGACGGCAGTGTGCTGGGCAGGGGCCACAACATGAGGTTCCAGAAGGGCTCCGCCACCCTGCACGGCGAGATCTCCACCCTGGAGAACTGTGGCAGGCTGGAGGGCAAGGTGTACAAGGACACCACCCTGTACACCACCCTGTCCCCTTGTGACATGTGTACCGGCGCTATCATCATGTACGGCATCCCTAGGTGTGTGGTGGGCGAGAACGTGAACTTCAAGTCCAAGGGCGAGAAGTACCTGCAAACCAGGGGCCACGAGGTGGTGGTTGTTGACGATGAGAGGTGTAAGAAGATCATGAAGCAGTTCATCGACGAGAGGCCTCAGGACTGGTTCGAGGATATCGG

B. Heat Stabilized CD Gene.

Additional modifications were made to enhance the stability of thecytosine deaminase. Genetic enhancements to the wild type yeast cytosinedeaminase gene were made to include three positional mutations whichchange three amino acids (A23L, I140L and V108I) to increase thermalstability of the yeast cytosine deaminase protein.

The following primer pairs were used in the generation of the gene forthe cytosine deaminase polypeptide of the disclosure:

Site Directed Mutagenesis Primers:

Primers sense: (SEQ ID NO: 45)5′-tcgaggatatcggcgagtgaaacccgttattctttttggc-3′ Primers antisense:(SEQ ID NO: 46) 5′-gccaaaaagaataacgggtttcactcgccgatatcctcga-3′Primers sense: (SEQ ID NO: 47)5′tcggcgagtgatccggcggcggcgcctccggcggcggcgcctccggcggcggcgcctccggcggcggcgccaacccgttatt-3′ Primers antisense: (SEQ ID NO: 48)5′-aataacgggttggcgccgccgccggaggcgccgccgccggaggcgccgccgccggaggcgccgccgccggatcactcgccga-3′

To increase the stability of the native yeast CD protein, three aminoacid substitutions were engineered into the protein. These substitutionswere alone or in combination with human codon optimization.

The three amino acid substitutions are: A23L, V108I, I140L. A sequenceencoding these substitutions is shown below.

(SEQ ID NO: 3) ATGGTGACAGGGGGAATGGCAAGCAAGTGGGATCAGAAGGGTATGGACATTGCCTATGAGGAGGCG TTA TTAGGTTACAAAGAGGGTGGTGTTCCTATTGGCGGATGTCTTATCAATAACAAAGACGGAAGTGTTCTCGGTCGTGGTCACAACATGAGATTTCAAAAGGGATCCGCCACACTACATGGTGAGATCTCCACTTTGGAAAACTGTGGGAGATTAGAGGGCAAAGTGTACAAAGATACCACTTTGTATACGACGCTGTCTCCATGCGACATGTGTACAGGTGCCATCATCATG TATGGTATTCCACGCTGTGTCATC GGTGAGAACGTTAATTTCAAAAGTAAGGGCGAGAAATATTTACAAACTAGAGGTCACGAGGTTGTTGTTGTTGACG ATGAGAGGTGTAAAAAG TTAATGAAACAATTTATCGATGAAAGACCTCAG GATTGGTTTGAAGATATTGGTGAGTAG 

The encoded polypeptide comprises the following sequence (substitutedamino acids in underlined):

(SEQ ID NO: 4) 1 MVTGGMASKWDQKGMDIAYEEA L LGYKEGGVPIGGCLINNKDGSVLGRGHNMRFQKGSAT 61 LHGEISTLENCGRLEGKVYKDTTLYTTLSPCDMCTGAIIMYGI PRCV IGENVNFKSKGEK 121 YLQTRGHEVVVVDDERCKK L MKQFIDERPQDWFEDIGE-

Final construct design that integrates 3 amino acid substitutionsA23L/V108I/I140L utilizing preferred codons and uses preferred humancodon usage for entire sequence (this gene is called CDopt+3pt [aka CD2](SEQ ID NO:49):

1 ATGGTGACCGGCGGCATGGCCTCCAAGTGGGATCAAAAGGGCA TGGATATCGCTTACGAG 61GAGGCCCTGCTGGGCTACAAGGAGGGCGGCGTGCCTATCGGCG GCTGTCTGATCAACAAC 121AAGGACGGCAGTGTGCTGGGCAGGGGCCACAACATGAGGTTCC AGAAGGGCTCCGCCACC 181CTGCACGGCGAGATCTCCACCCTGGAGAACTGTGGCAGGCTGG AGGGCAAGGTGTACAAG 241GACACCACCCTGTACACCACCCTGTCCCCTTGTGACATGTGTA CCGGCGCTATCATCATG 301TACGGCATCCCTAGGTGTGTGATCGGCGAGAACGTGAACTTCA AGTCCAAGGGCGAGAAG 361TACCTGCAAACCAGGGGCCACGAGGTGGTGGTTGTTGACGATG AGAGGTGTAAGAAGCTG 421ATGAAGCAGTTCATCGACGAGAGGCCTCAGGACTGGTTCGAGG ATATCGGCGAGTGATAA

T5.0002 refers to the above modified CD when inserted into the plasmidvector pAC3 which encodes the RCR with IRES. Underlined codons denotespreferred codons for amino acid substitutions.

Protein translation sequence alignment indicates preferred codon changesand amino acid substitutions result in desired protein structure:

CD-optimized sequence design (human codon preference+3 amino acidsubstitutions)

(SEQ ID NO: 50)

ACGAGGAGGCCCTGCTGGGCTACAAGGAGGGCGGCGTGCCTATCGGCGGCTGTCTGATCAACAACAAGGACGGCAGTGTGCTGGGCAGGGGCCACAACATGAGGTTCCAGAAGGGCTCCGCCACCCTGCACGGCGAGATCTCCACCCTGGAGAACTGTGGCAGGCTGGAGGGCAAGGTGTACAAGGACACCACCCTGTACACCACCCTGTCCCCTTGTGACATGTGTACCGGCGCTATCATCATGTACGGCATCCCTAGGTGTGTGATCGGCGAGAACGTGAACTTCAAGTCCAAGGGCGAGAAGTACCTGCAAACCAGGGGCCACGAGGTGGTGGTTGTTGACGATGAGAGGTGTAAGAAGCTGATGAAGCAGTTCATCGACGAGAGGCCTCAGGACTGGTTCGAGG

GG

C. Construction of CD-UPRT Fusion Gene (CDopt+3pt-UPRT, [Aka CDopt-UPRTand CD2-UPRT], T5.0003 in the pAC3 Plasmid RCR Vector).

A fusion construct was also developed comprising a CD polypeptide asdescribed above linked to a UPRT polypeptide to generate aCD-optimized-UPRT sequence using Scheme I as set forth in FIG. 10A. Thefollowing primers were used to delete the stop-start between the CD andUPRT.

Primer sequences: Primer Name Primer Sequence (5′ to 3′)(SEQ ID NO:)del118-123 5′-tcgaggatatcggcgagtgaaacccgttattctttttggc-3′ (51)del118-123-antisense 5′-gccaaaaagaataacgggtttcactcgccgatatcctcga-3′ (52)Energy Duplex Energy at Cost of Primer Name Length (nt.) Tm 68° C.Mismatches del118-123 40 79.06° C. −44.37 kcal/mole 21.1%del118-123-antisense 40 79.06° C. −47.95 kcal/mole 20.3% Primer NamePrimer-Template Duplex del118-123(SEQ ID5′-tcgaggatatcggcgagtga------aacccgttattctttttggc-3′ NOs: 51 and 53,   ||||||||||||||||||||      |||||||||||||||||||| respectively)ccaagctcctatagccgctcactatctacttgggcaataagaaaaaccgaagdel118-123-antisenseggttcgaggatatcggcgagtgatagatgaacccgttattctttttggcttc(SEQ ID NO: 54 and 52    ||||||||||||||||||||      ||||||||||||||||||||respectively) 3′-agctcctatagccgctcact------ttgggcaataagaaaaaccg

The resulting fusion polynucleotide comprises 1296 bp and the sequenceset forth immediately below:

(SEQ ID NO: 55)

ACGAGGAGGCCCTGCTGGGCTACAAGGAGGGCGGCGTGCCTATCGGCGGCTGTCTGATCAACAACAAGGACGGCAGTGTGCTGGGCAGGGGCCACAACATGAGGTTCCAGAAGGGCTCCGCCACCCTGCACGGCGAGATCTCCACCCTGGAGAACTGTGGCAGGCTGGAGGGCAAGGTGTACAAGGACACCACCCTGTACACCACCCTGTCCCCTTGTGACATGTGTACCGGCGCTATCATCATGTACGGCATCCCTAGGTGTGTGATCGGCGAGAACGTGAACTTCAAGTCCAAGGGCGAGAAGTACCTGCAAACCAGGGGCCACGAGGTGGTGGTTGTTGACGATGAGAGGTGTAAGAAGCTGATGAAGCAGTTCATCGACGAGAGGCCTCAGGACTGGTTCGAGGATATCGGCGAGAACCCGTTATTCTTTTTGGCTTCTCCATTCTTGTACCTTACATATCTTATATATTATCCAAACAAAGGGTCTTTCGTTAGCAAACCTAGAAATCTGCAAAAAATGTCTTCGGAACCATTTAAGAACGTCTACTTGCTACCTCAAACAAACCAATTGCTGGGTTTGTACACCATCATCAGAAATAAGAATACAACTAGACCTGATTTCATTTTCTACTCCGATAGAATCATCAGATTGTTGGTTGAAGAAGGTTTGAACCATCTACCTGTGCAAAAGCAAATTGTGGAAACTGACACCAACGAAAACTTCGAAGGTGTCTCATTCATGGGTAAAATCTGTGGTGTTTCCATTGTCAGAGCTGGTGAATCGATGGAGCAAGGATTAAGAGACTGTTGTAGGTCTGTGCGTATCGGTAAAATTTTAATTCAAAGGGACGAGGAGACTGCTTTACCAAAGTTATTCTACGAAAAATTACCAGAGGATATATCTGAAAGGTATGTCTTCCTATTAGACCCAATGCTGGCCACCGGTGGTAGTGCTATCATGGCTACAGAAGTCTTGATTAAGAGAGGTGTTAAGCCAGAGAGAATTTACTTCTTAAACCTAATCTGTAGTAAGGAAGGGATTGAAAAATACCATGCCGCCTTCCCAGAGGTCAGAATTGTTACTGGTGCCCTCGACAGAGGTCTAGATGAAAACAAGTATCTAGTTCCAGGGTTGGGTGACTTTGGTGACAG

GGGG

D. Construction of CD-Linker UPRT Fusion Gene (CDopt+3pt-LINK-UPRT [AkaCDopt-LINKER-UPRT and CD2-L-UPRT].

A fusion construct was also developed by cloning a linker(Ser-Gly-Gly-Gly-Gly)₄ (SEQ ID NO:56) domain between and in frame withthe CD polypeptide and the UPRT polypeptide to generated aCD-optimized-linker-UPRT sequence using Scheme II as depicted in FIG.10B. The following primers were used to insert the linker.

Primer Name Primer Sequence (5′ to 3′)(SEQ ID NO:) ins_60 nt_after_4775′- tcggcgagtgatccggcggcggcgcctccggcggcggcgcctccggcggcggcgcctccggcggcggcgccaacccgttatt-3′ (57) ins_60 nt_after_477- 5′-antisense aataacgggttggcgccgccgccggaggcgccgccgccggaggcgccgccgccggaggcgccgccgccggatcactcgccga-3′ (58) Energy Cost LengthDuplex Energy at of Primer Name (nt.) Tm 68° C. Mismatchesins_60 nt_after_477 82 79.77° C. −30.19 kcal/mole 83.3%ins_60 nt_after_477- 82 79.77° C. −32.31 kcal/mole 82.2% antisense

The resulting construct has size: 1356 bp and the sequence immediatelybelow:

(SEQ ID NO: 59)

ACGAGGAGGCCCTGCTGGGCTACAAGGAGGGCGGCGTGCCTATCGGCGGCTGTCTGATCAACAACAAGGACGGCAGTGTGCTGGGCAGGGGCCACAACATGAGGTTCCAGAAGGGCTCCGCCACCCTGCACGGCGAGATCTCCACCCTGGAGAACTGTGGCAGGCTGGAGGGCAAGGTGTACAAGGACACCACCCTGTACACCACCCTGTCCCCTTGTGACATGTGTACCGGCGCTATCATCATGTACGGCATCCCTAGGTGTGTGATCGGCGAGAACGTGAACTTCAAGTCCAAGGGCGAGAAGTACCTGCAAACCAGGGGCCACGAGGTGGTGGTTGTTGACGATGAGAGGTGTAAGAAGCTGATGAAGCAGTTCATCGACGAGAGGCCTCAGGACTGGTTCGAGGATATCGGCGAGTCCGGCGGCGGCGCCTCCGGCGGCGGCGCCTCCGGCGGCGGCGCCTCCGGCGGCGGCGCCAACCCGTTATTCTTTTTGGCTTCTCCATTCTTGTACCTTACATATCTTATATATTATCCAAACAAAGGGTCTTTCGTTAGCAAACCTAGAAATCTGCAAAAAATGTCTTCGGAACCATTTAAGAACGTCTACTTGCTACCTCAAACAAACCAATTGCTGGGTTTGTACACCATCATCAGAAATAAGAATACAACTAGACCTGATTTCATTTTCTACTCCGATAGAATCATCAGATTGTTGGTTGAAGAAGGTTTGAACCATCTACCTGTGCAAAAGCAAATTGTGGAAACTGACACCAACGAAAACTTCGAAGGTGTCTCATTCATGGGTAAAATCTGTGGTGTTTCCATTGTCAGAGCTGGTGAATCGATGGAGCAAGGATTAAGAGACTGTTGTAGGTCTGTGCGTATCGGTAAAATTTTAATTCAAAGGGACGAGGAGACTGCTTTACCAAAGTTATTCTACGAAAAATTACCAGAGGATATATCTGAAAGGTATGTCTTCCTATTAGACCCAATGCTGGCCACCGGTGGTAGTGCTATCATGGCTACAGAAGTCTTGATTAAGAGAGGTGTTAAGCCAGAGAGAATTTACTTCTTAAACCTAATCTGTAGTAAGGAAGGGATTGAAAAATACCATGCCGCCTTCCCAGAGGTCAGAATTGTTACTGGTGCCCTCGACAGAGGTCTAGATGAAAACAAGTATCTAGTTCCAGGGTTGGGTGACTTTGGTGACAGATACTACT

CTCCAGAAAAAGGGGGG

E. Construction of CD-OPRT Fusion Gene (CDopt+3pt-OPRT [Aka CDopt-OPRTand CD2-OPRT], T5.0004 when Inserted into the pAC3 Plasmid RCR Vector).

A fusion construct was also developed comprising a CD polypeptide asdescribed above linked to an OPRT polypeptide to generated aCD-optimized-OPRTase (CD humanized+3ptmutation+OPRTase functional domainhuman) using Scheme III as shown in FIG. 10C.

The resulting construct comprises a size of 1269 bp and the sequenceimmediately below:

(SEQ ID NO: 60)

ACGAGGAGGCCCTGCTGGGCTACAAGGAGGGCGGCGTGCCTATCGGCGGCTGTCTGATCAACAACAAGGACGGCAGTGTGCTGGGCAGGGGCCACAACATGAGGTTCCAGAAGGGCTCCGCCACCCTGCACGGCGAGATCTCCACCCTGGAGAACTGTGGCAGGCTGGAGGGCAAGGTGTACAAGGACACCACCCTGTACACCACCCTGTCCCCTTGTGACATGTGTACCGGCGCTATCATCATGTACGGCATCCCTAGGTGTGTGATCGGCGAGAACGTGAACTTCAAGTCCAAGGGCGAGAAGTACCTGCAAACCAGGGGCCACGAGGTGGTGGTTGTTGACGATGAGAGGTGTAAGAAGCTGATGAAGCAGTTCATCGACGAGAGGCCTCAGGACTGGTTCGAGGATATCGGCGAGGCGGTCGCTCGTGcagctttggggccattggtgacgggtctgtacgacgtgcaggctttcaagtttggggacttcgtgctgaagagcgggctttcctcccccatctacatcgatctgcggggcatcgtgtctcgaccgcgtcttctgagtcaggttgcagatattttattccaaactgcccaaaatgcaggcatcagttttgacaccgtgtgtggagtgccttatacagctttgccattggctacagttatctgttcaaccaatcaaattccaatgcttattagaaggaaagaaacaaaggattatggaactaagcgtcttgtagaaggaactattaatccaggagaaacctgtttaatcattgaagatgttgtcaccagtggatctagtgttttggaaactgttgaggttcttcagaaggagggcttgaaggtcactgatgccatagtgctgttggacagagagcagggaggcaaggacaagttgcaggcgcacgggatccgcctccactcagtgtgtacattgtccaaaatgctggagattctcgagcagcagaaaaaagttgatgctgagacagttgggagagtgaagaggtttattcaggagaatgtctttgtggcagcgaatcataatggttctcccctttctataaaggaagcacccaaagaa

ATAGATAAAATAAAAGATTTTATTTAGTCTCCAGAAAAAGGGGGG

F. Construction of CD-Linker-OPRT Fusion Gene (CDopt+3pt-LINK-OPRT, [AkaCDopt-LINKER-OPRT and CD2-L-OPRT], T5.0005 in the pAC3 Plasmid RCRVector).

A fusion construct was also developed by cloning a linker(Ser-Gly-Gly-Gly-Gly)₄) (SEQ ID NO:56) domain between and in frame withthe CD polypeptide and the OPRT polypeptide to generated aCD-optimized-linker-OPRT sequence using Scheme IV as shown in FIG. 10D.

The resulting construct comprises a size of 1329 bp and the sequenceimmediately below:

(SEQ ID NO: 61)

ACGAGGAGGCCCTGCTGGGCTACAAGGAGGGCGGCGTGCCTATCGGCGGCTGTCTGATCAACAACAAGGACGGCAGTGTGCTGGGCAGGGGCCACAACATGAGGTTCCAGAAGGGCTCCGCCACCCTGCACGGCGAGATCTCCACCCTGGAGAACTGTGGCAGGCTGGAGGGCAAGGTGTACAAGGACACCACCCTGTACACCACCCTGTCCCCTTGTGACATGTGTACCGGCGCTATCATCATGTACGGCATCCCTAGGTGTGTGATCGGCGAGAACGTGAACTTCAAGTCCAAGGGCGAGAAGTACCTGCAAACCAGGGGCCACGAGGTGGTGGTTGTTGACGATGAGAGGTGTAAGAAGCTGATGAAGCAGTTCATCGACGAGAGGCCTCAGGACTGGTTCGAGGATATCGGCGAGTCCGGCGGCGGCGCCTCCGGCGGCGGCGCCTCCGGCGGCGGCGCCTCCGGCGGCGGCGCCGCGGTCGCTCGTGcagctttggggccattggtgacgggtctgtacgacgtgcaggctttcaagtttggggacttcgtgctgaagagcgggctttcctcccccatctacatcgatctgcggggcatcgtgtctcgaccgcgtcttctgagtcaggttgcagatattttattccaaactgcccaaaatgcaggcatcagttttgacaccgtgtgtggagtgccttatacagctttgccattggctacagttatctgttcaaccaatcaaattccaatgcttattagaaggaaagaaacaaaggattatggaactaagcgtcttgtagaaggaactattaatccaggagaaacctgtttaatcattgaagatgttgtcaccagtggatctagtgttttggaaactgttgaggttcttcagaaggagggcttgaaggtcactgatgccatagtgctgttggacagagagcagggaggcaaggacaagttgcaggcgcacgggatccgcctccactcagtgtgtacattgtccaaaatgctggagattctcgagcagcagaaaaaagttgatgctgagacagttgggagagtgaagaggtttattcaggagaatgtctttgtggcagcgaatcataatggttctcccctttctataaaggaagcacccaaagaactcaGCTT

AATAAAAGATTTTATTTAGTCTCCAGAAAAAGGGGGG

FIG. 4 demonstrates that higher levels of the human codon optimized withthe three mutations for higher stability are observed compared to wildtype yCD protein in infected U-87 cells.

Example 3. Vector Production by Transient Transfection

Vector can be produced in a number of ways, but the first step is tointroduce the DNA vector into cells to allow production of infectiousparticles, that can then be harvested from the cell supernatant. Onceinfectious particles have been generated other methods of production canbe implemented by those skilled in the art. Vector particles weregenerated by transient transfection of 293T cells (Pear et al. Proc NatlAcad Sci USA. 90:8392-8396 1993).

The 293T cells were thawed and put into culture, then passaged twice inT-75 flasks containing 15 mL of the DMEM medium that was prepared bymixing DMEM High Glucose medium (Hyclone #30081, 500 mL) with FBS(Hyclone # SH30070, 50 mL), L-Glutamine (Cellgro #25-005-CI, 5 mL), NEAA(Hyclone #SH30238, 5 mL), and Penicillin-strep (Cellgro #30-002-CI, 5mL). The flasks were incubated at 37° C. and 5% CO₂. After the 3^(rd)passage cells were seeded in 6 T-25's, each containing 5 mL of themedium, at a cell density of 1.8×10⁶ cells/T-25 (or 7.2×10⁴ cells/cm²).One day after seeding the T-25's, the cells were transfected with theT5.0002 plasmid that expressed the viral vector using the CalciumPhosphate Transfection Kit from Promega (Cat # E1200). Eighteen hoursfollowing transfection, the media in one set of the flasks (3 flaskseach set) were replaced with fresh medium containing 10 mM NaB. Themedia in the 2nd set of the flasks were not replaced, which served as acontrol (zero NaB). Eight hours post NaB treatment the media in allflasks were replaced with the fresh medium containing no NaB. Theexpression was allowed to continue for both sets of flasks until thenext day (22 hours duration). The supernatants from both sets of flaskswere harvested and assayed for their titers by qPCR expressed inTransducing Units (TU)/ml (see Example 4).

The titer results are shown in the following table.

Second titer (after storing Condition First titer at −80° C. for 68days) Without NaB 1.5 (±0.05) × 10⁶ TU/mL  1.2 (±0.2) × 10⁶ TU/mL 10 mMNaB  1.4 (±0.3) × 10⁶ TU/mL 7.0 (±0.14) × 10⁵ TU/mL TU = transductionunit

Subsequent vector preparations were produced in this manner, withoutsodium butyrate. Other vector plasmids (Table 2) have been used in thesame way to generate vector preparations with titers between 1E5 TU/mland 1E7 TU/ml. Such material can be further purified and concentrated,if desired, as described below see also: U.S. Pat. No. 5,792,643; T.Rodrigues et al. J Gene Med 9:233 2007.

In certain embodiments of the disclosure the dosing was calculated bygrams of brain weight. In such embodiments, the dosing of a replicationcompetent retroviral vector of the disclosure useful in the methods fortreatment can range from 10⁴ to 10⁶ TU per gram brain weight.

Example 4. Quantitative PCR Tittering Assay

The functional vector concentration, or titer, is determined using aquantitative PCR-based (qPCR) method. In this method, vector is titeredby infecting a transducible host cell line (e.g. PC-3 human prostaticcarcinoma cells, ATCC Cat # CRL-1435) with a standard volume of vectorand measuring the resulting amount of provirus present within the hostcells after transduction. The cells and vector are incubated understandard culturing condition (37° C., 5% CO₂) for 24 hr to allow forcomplete infection prior to the addition of the anti-retroviral AZT tostop vector replication. Next, the cells are harvested from the culturedish and the genomic DNA (gDNA) is purified using an Invitrogen PurelinkgDNA purification kit and eluted from the purification column withsterile RNase-/DNase-free water. The A₂₆₀/A₂₈₀ absorbance ratio ismeasured on a spectrophotometer to determine the concentration andrelative purity of the sample. The gDNA concentrations are normalizedwith additional RNase-/DNase-free water to the lowest concentration ofany given set of gDNA preparations such that the input DNA for the qPCRis constant for all samples analyzed. Genomic DNA purity is furtherassessed by electrophoresis of an aliquot of each sample on an ethidiumbromide stained 0.8% agarose gel. If the sample passes an A₂₆₀/A₂₈₀absorbance range of 1.8-2.0 and shows a single band of gDNA, then thesample is ready for qPCR analysis of provirus copy number of the vector.Using primers that interrogate the LTR region of the provirus(reverse-transcribed vector DNA and vector DNA that is integrated intothe host gDNA), qPCR is performed to estimate the total number oftransduction events that occurred when the known volume of vector wasused to transduce the known number of cells. The number of transductionevents per reaction is calculated from a standard curve that utilizes atarget-carrying plasmid of known copy-number that is serial diluted from10⁷ to 10 copies and measured under identical qPCR conditions as thesamples. Knowing how many genomic equivalents were used for each qPCRreaction (from the concentration previously determined) and how manytransduction events that occurred per reaction, we determine the totalnumber of transduction events that occurred based on the total number ofcells that were present at the time of transduction. This value is thetiter of the vector after dilution into the medium containing the cellsduring the initial transduction. To calculate the corrected titer value,the dilution is corrected for by multiplying through by the volume ofculture and the volume of titer divided by the volume of titer. Theseexperiments are performed in replicate cultures and analyzed by qPCRusing triplicate measurements for each condition to determine an averagetiter and with its associated standard deviation and coefficient ofvariance.

Example 5. Vector Testing

In order to be effective vector constructs and their derived infectiousparticles need to: (1) make good titer of virus by transienttransfection (see Examples 3 and 4); (2) be stable upon multiplepassages; (3) kill cells efficiently in the presence of 5-FC; and (4)express enzyme activity upon infection of target cells. Example 3 showsthat useful titers can be obtained from the vectors.

Genetic Stability of Viral Vectors.

To demonstrate the stability the following experiment was performed.Approximately 10⁶ naïve U-87 cells were initially infected with theviral vector at an MOI of 0.01, and grown until fully infected tocomplete a single cycle of infection. Supernatant is then repassed ontouninfected cells and the cycle repeated. In this experiment, twelvecycles have been completed in duplicate trials (FIG. 5 shows one of eachof the duplicate trials; the other duplicates gave similar results).Genomic stability of the yCD2 or other transgene sequence is assessed byPCR amplification of the integrated provirus from the infected cellsusing MLV specific primers flanking the transgene insertion site. Theappearance of any bands smaller than full-length amplicon would be anindicator of vector instability. FIG. 5 demonstrates that a vector ofthe disclosure (T5.0007—comprising the modified vector and CDheterologous polynucleotide) maintains stability for more passages thanpACE-CD. Furthermore T5.0003 is somewhat less stable while T5.0004 andT5 appear about as stable as pACE-CD. pACE-CD has been used in mousetumor studies and shows good anti-tumor effects in mouse models. Howevera more stable viral genome will be much more potent and long lasting intreatment of animals and humans, especially if multiple cycles of 5-FCtreatment are required. Both T5.0001 and T5.0002 are markedly morestable than even T5.0007, showing that silent changes in a proteincoding sequence or small changes that result in point mutations can leadto unexpectedly superior properties with more stable vector genomes.

Cell Killing Experiments.

The Cell Titer 96 Aqueous One Solution Cell Proliferation Assay (MTS) isa colorimetric method for determining the number of viable cells inproliferation assays. We have utilized this assay to determine cellgrowth kinetics, as well as to determine the dose response of variouscell lines to 5-Fluorocytosine (5-FC) and 5-Fluorouracil (5-FU).

Cells 100% infected with vector were seeded at 1000 cells/well in96-well plates. They were monitored over an eight day period followingtreatment with various concentrations of 5-FC (5-FU for controls). Ananalysis of their cell growth was assessed every two days utilizingPromega's Cell Titer 96 AQueous One Solution reagent (MTS). Briefly, 20μl of MTS was mixed with 100 μl media (as recommended by themanufacturer) and added to the samples in the 96-well plate. The sampleswere incubated for 60 minutes in a 37° C./5% CO₂ incubator. Thereafter,absorbance readings were taken on a plate reader at a 490 nm wavelength.The plates were then discarded.

FIG. 6A shows the results of an experiment that demonstrates that thecytosine deaminase in cells expressing the yCD2 protein is at least asactive as that from cells expressing the wild type yCD protein, byperforming 5-FC titrations on U-87 cells infected either with AC3-yCD2(vector) or AC3-yCD (vector). Briefly, U-87 cells 5 days post infectionat a multiplicity of infection of 0.1 (i.e. 100% infected) with eitherAC3-yCD (wild type CD) vector or AC3-yCD2 (thermostabilized & codonoptimized) vector were subject to increasing amounts of 5-FC or 0.1 mMof 5-FU as a positive control for 8 days. On day 8, cell cultures wereassessed for viability using an MTS assay (Promega Cell Titer 96 AQUEOUSOne Solution Proliferation Assay). Data shows comparable killing betweenthe two retroviral vectors at increasing doses of 5-FC treatment.

In similar in-vitro cell culture experiments with RG2 cells (ATCC Cat #CRL-2433), the RG2 cell line was transduced with 5 different vectors(pACE-CD, T5.0001, T5.0002, T5.0004, and T5.0007). It was subsequentlysubject to increasing concentrations of 5-FC (5-FU for controls) for 8days and monitored as described above. The results are shown in FIG. 2.Concentrations of 0.01 mM were sufficient to induce complete killingthroughout all vectors tested with the exception of wild type-yeastCytosine Deaminase (pACE-yCD). It was less sensitive and required 1.0 mMof 5-FC for complete killing.

CD Expression Assay.

U87 cells were transduced at a multiplicity of infection (MOI) of 0.1,cultivated for 5 days to allow viral spread and cells from day 5 posttransduction were harvested. The cells were then collected bycentrifugation at 800×g for 5 min. The supernatant was aspirated awayfrom the cell pellet and washed with 5 mL of phosphate buffered saline(PBS) and again centrifuged at 800×g for 5 min. The resulting cellpellet was taken up in 1.5 mL of PBS, resuspended by passage through apipette tip and placed in a freezer at −20 C. Cells were lysed by afreeze/thaw method. Previously resuspended cells were allowed to thaw atroom temperature, passed through a pipette tip, mixed with proteaseinhibitor cocktail and again refrozen at −20 C. Previous to the enzymeassay, the sample was again thawed at room temperature and passedthrough a pipette tip. The suspension was then centrifuged at 14,000 rpmin a tabletop centrifuge for 5 min. The supernatant was decanted awayfrom the pellet and placed in a fresh eppendorf tube and placed on ice.

yCD enzyme activity was assessed by using an HPLC assay. The HPLC assaywas performed on a Shimadzu LC20AT unit connected in series with aphotoarray detector and autoinjector. The solid phase was a Hypersil BDSCie HPLC column with a 5 um sphere size and 4.0×250 mm columndimensions. The mobile phase was 50 mM ammonium phosphate, pH 2.1,containing 0.01% tert-butylammonium perchlorate and 5% methanol; thesystem was equilibrated at 22 C. All reagents were ACS grade andsolvents were HPLC grade. A reaction mix was made consisting of 800 μLwith a final concentration of 0.125 mg/mL 5FC (1 mM) in PBS and placedin a 1.5 mL autosampler vial. The reaction was then initiated by adding200 uL of each cell lysate. The reaction/autosampler vials were placedin the auto sampler and 5 uL of the reaction mixture was injected. Timepoints were taken periodically by retrieving a 5 uL aliquot from eachreaction vial and analyzing on the HPLC column. The conversion rates of5FC to 5FU were calculated by comparing the peak areas with knownamounts from a previously generated standard curve of 5FU. The rate of5FC conversion to 5FU was derived by plotting the amount of 5FU (innmol) generated against its corresponding time interval. Proteinconcentration for the cell sample was derived and the Specific Activityof the cell lysate samples were calculated by dividing the conversionrate (nmol/min) by the amount of protein used in the assay in mg. FIG.6B shows the specific activity of various vectors after 5 days ontransduction at an MOI of 0.1. The data demonstrate that pACE-yCD(T5.0000)<pAC3-yCD1 (T5.0001)<pAC3-CD2 (T5.0002) in terms of thespecific activity of cytosine deaminase in tissue culture cells.

Example 6. Vector Purification and Concentration

A vector of the disclosure is manufactured by transient transfection on293T cells (Example 3), followed by harvesting of the cell supernatant,filtration, benzonase treatment, diafiltration/concentration anddialysis. A further chromatography column step may be included, known tothose skilled in the art (see for example U.S. Pat. No. 5,792,643; T.Rodriguez et al. J Gene Med 9:233 2007; WO 2010/148203). Clinicalmaterial is released based on standard testing such as sterility,mycoplasma and endotoxins, plus product specific potency, strength, andidentity testing. Titer is determined as Transducing Units (TU) by PCRquantitation of integrated viral vector DNA in target cells (Example 4).The final product is targeted to have a titer of up to 10⁹ TU/mlformulated in isotonic Tris-buffered sucrose solution, as a sterileinjectable.

In general, to accurately and precisely determine the strength of vectorlots, a quantitative PCR-based titer assay has been developed (describedin general terms in example 4). The details of the assay procedureconsist of the following steps:

Transduction.

Transductions are performed in a 12-well plate format using the stablehuman prostate adenocarcinoma derived PC-3 cell line. For each testsample, three dilutions of un-titered vector preparation are used totransduce PC-3 cells in triplicate wells. Viral replication is stopped24 hours post-transduction with azidothymidine (AZT). Cells aremaintained for an additional 24-64 hours prior to harvesting and genomicDNA purification.

Genomic DNA Preparation.

Qiagen DNeasy DNA Minikits is used to prepare genomic DNA fromtransduced harvested cells as per the manufacturer's protocol. DNAconcentrations and quality are assessed by direct absorbance measurementusing UV/vis spectrophotometry to determine the A260 and A260/A280ratio.

Real-Time Quantitative PCR.

The BioRad CFX96 real-time PCR instrument or equivalent is used forperforming quantitative PCR. Provector copy numbers present in each testsample are measured by using specific DNA oligonucleotide primers inconjunction with a TaqMan probe designed to amplify the integrated, orpro-retroviral, U3/Psi packaging versus the CMV/Psi plasmid promoter.Vector titer is expressed relative to a copy number standard curve. Togenerate the vector copy number standard curve, genomic DNA from PC-3cells is spiked with a unique plasmid containing the pro-retroviralU3/Psi sequence. Vector test sample titers are obtained by calculatingthe number of transduced genomes in multiple dilutions using multiplereactions per dilution.

For each titer assessment, a non-template control (wells containing allcomponents except plasmid or genomic DNA) and a negative control (allcomponents including equivalent genomic DNA from non-transduced PC-3cells), is performed in triplicate. The titer values are expressed intransduction units per milliliter (TU/mL).

The potency of the vector of the disclosure is dependent on both thereplication of the vector and the resultant cytosine deaminase (CD)activity in target cells. Therefore the potency assay measures theincrease in CD activity over time as vector infection spreads in apreviously uninfected cell line in tissue culture. The assay measuresthe enzymatic activity of the transferred yCD2 protein in transducedcells during early, middle and late stages of infection by monitoringthe conversion of 5-fluorocytosine (5-FC) to 5-fluorouracil (5-FU),using reverse phase HPLC separation with UV detection. The increase ofCD activity over the course of the infection is a function of thepercent of cells infected over time and indicative of the TOCA 511vector's ability to replicate. CD activity based on the 5-FC to 5-FUconversion rate is measured for each time point in CD units per mg ofprotein (the specific activity, SA). The increase in SA is then plottedover time, and reflects both the increase in the percentage of cellstransduced as a result of viral replication in the culture, and theresultant transfer of CD activity. Accumulated data from multiple assaysand vector lots has been used to determine an appropriate specificationfor this increase in SA of CD, for product release. The assay has 1, 3and 5 day time points after an initial infection at an MOI of about 0.1and a non-infected control.

CD activity from late stage infected cells (day 5 time point) wascompared between lots to evaluate the use of this activity as anIdentity test. The assay includes the following steps:

Transductions.

Transductions are performed in multi-well plate format on U87 cells. Foreach transduction, three suitable dilutions are used and each performedin triplicate. Cells are harvested at 0, 1, 3 and 5 days posttransduction.

Set-Up of CD Reaction.

Cells are lysed and the total protein concentration determined using theBCA protein assay using BSA as a standard. For the yCD2 enzyme assay, anappropriate amount of cell lysate is added to buffer containing 5-FCsuch that the rate of 5-FU formation remains linear over 1-2 hours at37° C. The final volume for the reaction mixture is 100 μL. After 2 h,the enzyme reaction is terminated by the addition of trichloroaceticacid, briefly vortexed and prepared for subsequent HPLC analyses. Celllysates from non-transduced cells are used as a negative control while asimilar assay using samples from 100% infected cells is used as apositive control.

HPLC Analysis.

The terminated reaction mixture is centrifuged at 12,000 rpm for 5minutes at room temperature in a micro-centrifuge. The supernatant isthen decanted away from the pellet and passed through a 0.2p filter tofurther remove particulates before injection onto a reverse phase HPLCcolumn previously equilibrated with an aqueous based mobile phasecontaining phosphate buffer at a pH around 4.0. The chromatograms isfollowed at 260 nm and 280 nm to monitor both substrate consumption andproduct formation. Concentrations of either substrate or product aredetermined using the graphing and analysis capabilities of GraphPad bycomparing them to previously generated standard curves calculated fromknown substrate or product concentrations. Amounts of 5-FU generatedover 1-2 h are used to determine CD units of activity (1 unit of CDactivity is defined as the formation 1 nmol of 5-FU per min) and theSpecific Activity is calculated dividing this number by the amount ofprotein (from the cell lysate) used in the assay.

Example 7. Construction and Use of a Vector Encoding a Single ChainAntibody to CTLA-4 (CD 152)

Single chain antibodies are derived from known full antibody sequencesthat have a desired effect. Such sequences are available (e.g.WO2006048749, US2006165706, U.S. Pat. No. 7,034,121, Genbank AccessionNumbers DJ437648, CS441506, CS441500, CS441494, CS441488, thedisclosures of which are incorporated herein by reference). Suchconventional antibody gene sequences are converted into single chainantibody (scFv) sequences by commonly used methods known to thoseskilled in the art (see for example Gilliland et al. “Rapid and reliablecloning of antibody variable regions and generation of recombinantsingle chain antibody fragments.” Tissue Antigens 47, 1-20, 1996). Phagesingle chain antibodies to CTLA-4 are also available from screeningphage-scFv libraries directly (Pistillo et al. Tissue Antigens 55:2292000), and can be used directly for insertion into the replicatingretroviral vectors of the disclosure. Regardless of how the sequence isderived scFv are typically about 700-900 bp in length and aresynthesized by a commercial vendor (BioBasic) with a Psi1 site at the 5′end and compatible Not1 site at the 3′ end, as described previously.This sequence is then inserted into the replicating retroviral back bonefrom pAC3-yCD2 at the Psi1-Not1 sites after removal of the yCD2sequence. Vector is produced and titered as described, and furtherpurified if necessary as described above. Human and Mouse CTLA4 are veryhomologous in sequence and the replicating retrovirus of the disclosureis first tested in a suitable syngeneic immunocompetent mouse modelssuch as the CT26/Balb/c model and s91 mouse melanoma models, well knownto those skilled in the art (see for example Hodge et al J. Immunol.174:5994 2005). Outcome is measured by one or more of: modulation oftumor growth; lack of toxicity; generation of antitumor responses;shrinkage of remote lesions indicating systemic immunity. Doses are inthe range of 10³ to 10⁷ TU in mice. In patients the vector isadministered by intralesional injection into tumor, or by administrationinto the circulation that then carries the virus to the tumor. Doses arein the range of 10⁵ to 10¹¹ TU.

Example 8. Anti-Melanoma Efficacy Studies with Anti CD152 Single ChainAntibody Expressing Vector in a Mouse Melanoma Model

Objective.

The objective of this study is to assess the effect of a novel MLV basedreplication-competent retroviral vector carrying single chain antibodydirected against Cytotoxic T-Lymphocyte Antigen 4 (CTLA-4) also referredto as Cluster of differentiation 152 (CD152) sequence (pAC3-αCD152) onmelanoma growth, when delivered via intratumoral (IT) injection in DBA/2mice bearing subcutaneous melanoma (Cloudman S91).

Mice.

Female DBA/2 or BALB/c mice (age ˜8 weeks) are purchased from JacksonLaboratories (Bar Harbor, Me.). Mice are acclimated for 7 days afterarrival before start of studies.

Cells.

Cloudman S91 cells (ATCC, Manassas Va.) are a spontaneously arisingmelanoma derived from DBA/2 mice. Cells are cultured in Dulbecco'smodified Eagles medium with 10% fetal bovine serum, sodium pyruvate, andGlutamax (Hyclone, Logan Utah, and Invitrogen, San Diego Calif.). Cellsare resuspended in PBS (Hyclone, Logan Utah) for implantation. S91 cells(1E6 in 100 μL) are injected into the right flank of DBA/2 mice.

Vector.

Vectors preparations are made by transient transfection (or from aproducer cell line in HT1080 cells) with titers of approximately7E6TU/ml. For initial studies vector is not further purified orconcentrated. For follow on experiments to determine full dose responsecurves, high titer purified material is prepared with a titer expectedaround 10⁸/ml. Vector is administered IT in a volume of 50-100 μL and IVin 100 μL the total dose/mouse of approximately 7E5 TU/mouse. Vectorexpressing αCD152 is identified as Toca αCD152.

Tumor Implantation and Vector Injection.

Five groups of female DBA/2 (55 mice, 9-10 weeks of age) are implantedsubcutaneously with S91 melanoma cells (Day 0) and then dosed (day 4-7depending on growth rate of the S91 tumor; approximately 50-100 mm³)with vehicle (Groups 1), with control vector [AC3-GFP(V), (Group2),intratumor (IT) Toca αCD152 vector injection (Groups 3), or intravenousToca αCD152 vector injection (group 4). Group 5 mice have no tumorimplanted and are intravenously injected with Toca αCD152 only.

Data Analysis.

Tumor growth analysis is carried out to 2000 mm³ or to 60 days based onwhichever comes first. 10 mice from each group will be plotted for tumorsize over time. Statistical significance will be determined usinganalysis of variance (ANOVA). P values of <0.05 are consideredstatistically significant in all analyses, which are performed withPrism 5 statistical software (GraphPad Software) or equivalent. In-lifeobservations are also taken to assess any adverse events to αCD152expression during treatment.

Results.

Delivery of αCD152 by replicating MLV IT shows a statisticallysignificant retardation of growth compared to the controls. Delivery ofαCD152 by replicating MLV intravenously shows a statisticallysignificant retardation of growth compared to the controls abrogatesmelanoma burden from the DBA/2-Cloudman S91 mouse melanoma model.Further animal studies were performed as described more fully below.

Example 9. ACE-yCD2 Viral Vector is Therapeutic in an Intracranial HumanXenograft (U87) in Nude Mice

An intracranial xenograft model using the U87 human glioma cell line wasestablished to test RCR vector spread and biodistribution as well astherapeutic efficacy of RCR-vector mediated cytosine deaminase suicidegene therapy in a nude mouse host.

Following acclimation, mice were randomly assigned to one of 8 Treatmentgroups (see group description below). Seven groups underwentintracranial administration into the right striatum of 1×10⁵ U87 cellsadministered/mouse on Day 0. Group 8 mice were not implanted with tumor.At Day 5, mice were injected with Formulation Buffer only, or an RCRvector at 9×10⁵/5 ul, 9×10⁴/5 ul, or 9×10³/5 ul. Mice receiving novector, or vector at 9×10⁵/5 ul or 9×10³/5 ul were randomized to receive5-FC (500 mg/kg/day), administered as a single IP injection, beginningon Day 19, or no 5-FC. Mice receiving vector at mid dose all received5-FC (i.e., No separate control group for this dose). 5-FCadministration continued daily for 7 consecutive days followed by 15days of no treatment. Cycles of drug plus rest were repeated up to 4cycles. 10 mice from each group except group 8 were randomly assigned tothe survival analysis category. The remaining mice were sacrificedaccording to a predetermined schedule.

Group Assignments and Dose Levels N per Analysis Category (A) (B) TestDrug Survival Scheduled Group article Volume TX N analysis Sacrifice 1Form     5 ul none 4 4 before first buffer drug cycle 2 Form     5 ul5FC 10 10 buffer 3 T5.0002 9e5/5 ul PBS 10 10 4 T5.0002 9e5/5 ul 5FC 2510 3 before start of each cycle, 15 total 5 T5.0002 9e4/5 ul 5FC 10 10 6T5.0002 9e3/5 ul 5FC 25 10 3 before start of each cycle, 15 total 7T5.0002 9e3/5 ul PBS 10 10 8 none 5FC 15 3 before start NO of eachcycle, TUMOR 15 total Total Number of Animals 109 60 49

Intravenous dosing was done via injection into the tail vein.Intraperitoneal dosing was done via injection into the abdomen with caretaken to avoid the bladder. For intracranial injection mice wereanesthetized with isoflurane and positioned in a stereotaxic device withblunt ear bars. The skin was shaved and betadine was used to treat thescalp to prepare the surgical site. The animal was placed on a heatingpad and a scalpel used under sterile conditions to make a midlineincision through the skin. Retraction of the skin and reflection of thefascia at the incision site will allow for visualization of the skull. Aguide cannula with a 3 mm projection, fitted with a cap with a 3.5 mmprojection, will be inserted through a small burr hole in the skull andattached with dental cement and three small screws to the skull. Afterhardening of the cement, the skin will be closed with sutures. Theprojected stereotaxic coordinates are AP=0.5-1.0 mm, ML=1.8-2.0 mm,DV=3.0 mm. Exact stereotaxic coordinates for the cohort of animalsreceived will be determined in a pilot experiment (2-3 animals) byinjecting dye and determining its location. The animals will bemonitored during anesthesia recovery. Analgesics, buprenorphine, will beadministered subcutaneously (SC) before the end of the procedure thenbuprenorphine will be administered approximately every 12 hrs for up to3 days. Animals will be monitored on a daily basis. Cells or vector wereintracranially infused through an injection cannula with a 3.5 mmprojection inserted through the guide cannula. The rate was controlledwith a syringe pump fitted with a Hamilton syringe and flexible tubing.For cell injection, 1 microliter of cells was delivered at a flow rateof 0.2 microliters per minute (5 minutes total). For vector injection, 5microliters of vector was delivered at a flow rate 0f 0.33 microlitersper minute (15 minutes total).

Vector was delivered and calculated as transforming units (TU) per gramof brain weight to the mice. Using such calculation the translation ofdose can be calculated for other mammals including humans. FIG. 8 showsthe effect on vector dose in this mouse model.

Example 10. AC3-yCD2(V) is Therapeutic in a Syngeneic Mouse Model ofBrain Cancer

Additional experiments to demonstrate the methods and compositions ofthe disclosure in a syngeneic animal model were performed.

An intracranial implant model using the CT26 colorectal cancer cell linein syngeneic BALB/c mice was established to test RCR vector spread andbiodistribution as well as therapeutic efficacy of RCR-vector mediatedcytosine deaminase suicide gene therapy and its immunological impact.

This study included 129 animals, 0 Male, 119 Female and 10 contingencyanimals (10 Female). Following acclimation, mice were randomly assignedto one of 8 Treatment groups (see group description below). Seven groupsunderwent intracranial administration into the right striatum of 1×10⁴CT26 cells administered/mouse on Day 0. Group 8 mice were not implantedwith tumor. At Day 4, mice were injected with Formulation Buffer only,or vector at 9×10⁵/5 ul, 9×10⁴/5 ul, or 9×10³/5 ul. Mice receiving novector, or vector at 9×10⁵/5 ul or 9×10³/5 ul were randomized to receive5-FC (500 mg/kg/BID), administered by IP injection, beginning on Day 13,or no 5-FC. Mice receiving vector at mid dose received 5-FC (i.e. Noseparate control group for this dose). 5-FC administration continueddaily for 7 consecutive days followed by 10 days of no treatment. Cyclesof drug plus rest were repeated up to 4 cycles. 10 mice from each groupexcept group 8 were randomly assigned to the survival analysis category.The remaining mice were sacrificed according to a predeterminedschedule.

Naïve sentinel mice were co-housed with the scheduled sacrifice animalsand taken down at the same time points to assess vector transmittalthrough shedding.

Group Assignments and Dose Levels N per Analysis Category Test Drug (A)Survival (B) Scheduled (C) Group article Volume TX N analysis SacrificeSentinels 1 Form     5 ul PBS 4 4 before buffer first drug cycle 2 Form    5 ul 5FC 10 10 buffer 3 T5.0002 9e5/5 ul PBS 10 10 4 T5.0002 9e5/5ul 5FC 25 10 3 before 1 before start of start of each cycle, each cycle,15 total 5 total 5 T5.0002 9e4/5 ul 5FC 10 10 6 T5.0002 9e3/5 ul 5FC 2510 3 before 1 before start of start of each cycle, each cycle, 15 total5 total 7 T5.0002 9e3/5 ul PBS 10 10 8 none 5FC 15 3 before NO start ofTUMOR each cycle, 15 total Total Number of Animals 119 60 49 10

Intravenous dosing was done via injection into the tail vein.Intraperitoneal dosing was done via injection into the abdomen with caretaken to avoid the bladder. For intracranial administration, mice with aguide cannula with a 3.2 mm projection implanted into the rightstriatum, and fitted with a cap with a 3.7 mm projection were used. Theprojected stereotaxic coordinates are AP=0.5-1.0 mm, ML=1.8-2.0 mm,DV=3.2 mm (from bregma). Cells or vector were intracranially infusedthrough an injection cannula with a 3.7 mm projection inserted throughthe guide cannula. The rate was controlled with a syringe pump fittedwith a Hamilton syringe and flexible tubing.

For cell injection, 1 microliter of cells was delivered at a flow rateof 0.2 microliter per minute (5 minutes total). For vector injection, 5microliter of vector was delivered at a flow rate of 0.33 microliter perminute (15 minutes total).

Vector was delivered and calculated as transforming units (TU) per gramof brain weight to the mice. Using such calculation the translation ofdose can be calculated for other mammals including humans. FIG. 9 showsthe effect on vector dose in this mouse model when the vector isdelivered intracranially.

Example 11. Construction and Testing of RCR Vectors Expressing miR-128-1and miR128-2

Construction of Recombinant Replication Competent Retroviral VectorContaining a Heterologous Polynucleotide Sequence of HumanPri-miRNA-128-1.

The replication competent retroviral vector, pAC3-miR-128-1 expressingmiR-128-1 was derived from the backbone of pAC3-yCD2 described in one ofthe embodiment. The pAC3 backbone in the pAC3-miR-128-1 vector wasisolated by endonuclease digestion of the pAC3-yCD2 plasmid DNA with MluI and Not I to remove the IRES-yCD2 polynucleotide sequence. Thepolynucleotide DNA sequence of pri-miR-128-1 was obtained from theproduct sheet of the pEP-mir-128-1 expression vector (Cell BioLabs Inc.)(SEQ ID NO: 31). DNA sequence of pri-miR-128-1 was synthesized with aMlu I restriction enzyme site at the 5′ end and a Not I restrictionenzyme site at the 3′ end of the double-stranded DNA fragment forsubsequent insertion at the corresponding site in the Mlu I and Not Idigested pAC3-yCD2 plasmid DNA described above. The resulting construct,pAC3-miR-128-1, encodes 3 genes: the gag, the pol, and the env, and thenon-coding pri-miR-128-1 sequence (FIG. 11).

Vector stock was produced by transient transfection of thevector-encoding plasmid DNA into 293T cells using calcium phosphatemethod. Eighteen hours post transfection, the culture was replaced withfresh medium. Twenty-four hours post medium replacement, the supernatantcontaining the vector was collected and filtered through a 0.45 μmfilter and used immediately or stored in aliquots at −80° C. for lateruse. Twenty micro-liter of the collected vector stocks was used toinfect human prostate cancer cells, PC3. Twenty-four hours postinfection, AZT was added to the cells to inhibit further viralreplication. Forty-eight hours post infection, genomic DNA of infectedPC3 cells was extracted for titer assay. The titer of the vector stockswas determined by qPCR with an inclusion of standards of known copynumbers.

Construction of Recombinant Replication Competent Retroviral VectorContaining a Heterologous Polynucleotide Sequence of HumanPri-miRNA-128-2.

The replication competent retroviral vector, pAC3-miR-128-2 expressingmiR-128-2 was derived from the backbone of pAC3-yCD2 described in one ofthe embodiment. The pAC3 backbone in the pAC3-miR-128-1 vector wasisolated by endonuclease digestion of the pAC3-yCD2 plasmid DNA with MluI and Not I to remove the IRES-yCD2 polynucleotide sequence. Thepolynucleotide DNA sequence of pri-miR-128-2 was obtained from thesequence analysis of the expression vector Lenti-miR-128-2 expressingthe pri-miR128-2 (System Biosciences) (SEQ ID NO:32). DNA sequence ofpri-miR128-2 was synthesized with a Mlu I restriction enzyme site at the5′ end and a Not I restriction enzyme site at the 3′ end of thedouble-stranded DNA fragment for subsequent insertion at thecorresponding site in the Mlu I and Not I digested pAC3-yCD2 plasmid DNAdescribed above. The resulting construct, pAC3-miR-128-1, encodes 3genes: the gag, the pol, and the env, and the non-coding pri-miR-128-2sequence (FIG. 11).

Vector stock was produced by transient transfection of thevector-encoding plasmid DNA into 293T cells using calcium phosphatemethod. Eighteen hours post transfection, the culture was replaced withfresh medium. Twenty-four hours post medium replacement, the supernatantcontaining the vector was collected and filtered through a 0.45 □mfilter and used immediately or stored in aliquots at −80° C. for lateruse. Twenty micro-liter of the collected vector stocks was used toinfect human prostate cancer cells, PC3. Twenty-four hours postinfection, AZT was added to the cells to inhibit further viralreplication. Forty-eight hours post infection, genomic DNA of infectedPC3 cells was extracted for titer assay. The titer of the vector stockswas determined by qPCR with an inclusion of standards of known copynumbers.

Construction of Recombinant Replication Competent Retroviral VectorContaining Heterologous Polynucleotide Sequences of Human H1 Promoterand Human Pre-miRNA-128.

The replication competent retroviral vector, pAC3-miR-128-2 expressingmiR-128-2 was derived from the backbone of pAC3-yCD2 described in one ofthe embodiment. The pAC3 backbone in the pAC3-miR-128-1 vector wasisolated by endonuclease digestion of the pAC3-yCD2 plasmid DNA with MluI and Not I to remove the IRES-yCD2 polynucleotide sequence. Thepolynucleotide DNA sequence of the human H1 promoter was obtained fromthe product information of pSilencer 3.1 H1 hygro expression vector(Ambion), and the polynucleotide DNA sequence of the short hairpinstructured pre-miR-128-1 was obtained from thehttp:(//)www.mirbase.org/. DNA sequence of pre-miR128-1 linked to thehuman H1 promoter (SEQ ID NO: 33) was synthesized with a Mlu Irestriction enzyme site at the 5′ end and a Not I restriction enzymesite at the 3′ end of the double-stranded DNA fragment for subsequentinsertion at the corresponding site in the Mlu I and Not I digestedpAC3-yCD2 plasmid DNA described above. The resulting construct,pAC3-H1-shRNAmiR128, encodes 3 genes: the gag, the pol, and the env, andthe non-coding short hairpin structured pre-miR-128-1 sequence (FIG.11).

Vector stock was produced by transient transfection of thevector-encoding plasmid DNA into 293T cells using calcium phosphatemethod. Eighteen hours post transfection, the culture was replaced withfresh medium. Twenty-four hours post medium replacement, the supernatantcontaining the vector was collected and filtered through a 0.45

m filter and used immediately or stored in aliquots at −80° C. for lateruse. Twenty micro-liter of the collected vector stocks was used toinfect human prostate cancer cells, PC3. Twenty-four hours postinfection, AZT was added to the cells to inhibit further viralreplication. Forty-eight hours post infection, genomic DNA of infectedPC3 cells was extracted for titer assay. The titer of the vector stockswas determined by qPCR with an inclusion of standards of known copynumbers.

Analysis of Replication Kinetics of Recombinant Replication CompetentRetroviral Vector by qPCR Assay.

Currently, there are at least two common ways to obtain replicationkinetics of recombinant replication competent retroviral vector: (1)analysis of GFP expression with vectors expressing the GFP protein byflow cytometric analysis, and (2) reversed transcriptase assay bymeasuring the reverse transcriptase activity of the vector stockcollected from cultured medium of transduced cells. Titers assessed byDNA analysis of transduced cells provide the most reliable estimate ofthe functional titers as compared to titers obtained by RNA andtransgene expression in which titers were over-estimated andunder-estimated, respectively, (Sastry et al., 2002 Gene Therapy 9,1155-1162). The replication kinetics of viral spread correlates with thepercent of a cell population being transduced in which an integratedproviral DNA of the viral genome can be detected by qPCR with primersspecific to the viral sequence is being tested in culture. The presentassay requires equal amount of genomic DNA input from all time pointswithin the same vector tested and among various vectors if a comparisonof replication kinetics is being tested. The replication kinetics graphwas generated by plotting inversed C(t) values vs. time points. FIG. 12Aand FIG. 12B show comparisons of replication kinetics of variousrecombinant replication competent retroviral vectors. The assay issensitive to reveal the small difference in replication kinetics amongvarious vectors.

Testing of Replication Kinetics of miR-128 Containing RecombinantReplication Competent Retroviral Vectors in Culture.

In order to confirm that the incorporation of pri-miR-128-1,pri-miR-128-2 and H1-pre-miR-128-1 sequence, respectively, replicatesnormally, calculated volume of each vector stocks collected fromtransient transfection mentioned above was used to infect fresh humanfibrosarcoma cells, HT1080 and human glioma cells, U87-MG, respectively,at a MOI of 0.1. Transduced cells were passaged at day 3, 6 and 9 postinfection. At each time point, a portion of cells were collected forgenomic DNA extraction for qPCR. Dilutions of genomic DNA were made togenerate aliquots of genomic DNA with same concentration for equalamount of genomic in-put in qPCR. Replication kinetics of each vectorswere generated by plotting inversed C(t) values vs. time points. FIGS.12A and 12B show that all vectors tested replicated at similar kineticscompared to control MLV virus.

Testing of Expression of Mature miR-128 from Cells Transduced withmiR-128 Containing Recombinant Replication Competent Retroviral Vector.

In order to confirm the expression of miR-128 from cells transduced withmiR-128 containing recombinant replication competent retroviral vectors,cells from day 9 post infection at which the maximal infectivity hasreached (FIG. 12A and FIG. 12B) were expanded and harvested to extracttotal RNA for detection of mature miRNA expression. The results fromTaqman microRNA assay showed an over expression of mature miR-128 fromboth HT1080 and U87-MG cells transduced with pAC3-miR-128-1,pAC3-miR-128-2, and pAC3-H1-shRNAmiR128 vectors, respectively, comparedto untransduced cells (FIG. 13). In both cell lines, cells transducedwith pAC3-miR-128-1 and pAC3-H1-shRNAmiR128 vector expressed higherlevel of mature miR-128 than cells transduced with pAC3-miR-128-2vector.

Testing of Bmi-1 Expression from Cells Transduced with miR-128Containing Recombinant Replication Competent Retroviral Vectors toDemonstrate Target Engagement of miR-12.

Bmi-1 expression has been observed to be up-regulated in a variety ofhuman cancers including glioblastoma, and has been shown to be thetarget of miR-128. To confirm target engagement of miR-128, Bmi-1expression from cells transduced with pAC3-miR-128-1, pAC3-miR-128-2 andpAC3-H1-shRNAmiR128 vector, respectively, was detected by qRT-PCR. FIG.14 shows that U87-MG cells transduced with pAC3-miR-128-1,pAC3-miR-128-2 and pAC3-H1-shRNAmiR128 vector, respectively, expressedlower level of Bmi-1 than untransduced cells, whereas in HT1080 cells nosignificant difference was observed between transduced and untransducedcells. The data support the concept that miR-128 plays an importantfunctional role in the central nervous system.

Example 12: Construction and Testing of Recombinant ReplicationCompetent Retroviral Vector Containing Heterologous PolynucleotideSequences of IRES, yCD2, Human H1 Promoter and Human Pre-miR128-1

Construction.

The replication competent retroviral vector, pAC3-yCD2-H1-shRNAmiR128 isderived from the backbone of pAC3-yCD2 described in one of theembodiments. The pAC3-yCD2 backbone in the pAC3-yCD2-H1-shRNAmiR128vector is isolated by endonuclease digestion of the pAC3-yCD2 plasmidDNA with Not I. The polynucleotide DNA sequence of the human H1 promoteris obtained from the product information of pSilencer 3.1 H1 hygroexpression vector (Ambion), and the polynucleotide DNA sequence of theshort hairpin structured pre-miR-128-1 is obtained from thehttp:(//)www.mirbase.org/. DNA sequence of pre-miR128-1 linked to thehuman H1 promoter (SEQ ID NO: 34) is synthesized with a Not Irestriction enzyme site at both ends of the double-stranded DNA fragmentfor subsequent insertion at the corresponding site in Not I digestedpAC3-yCD2 plasmid DNA described above. The resulting construct,pAC3-H1-shRNAmiR128, encodes 4 genes: the gag, the pol, and the env, andthe yCD2, and the non-coding short hairpin structured pre-miR-128-1sequence (FIG. 11).

Vector stock is produced by transient transfection of thevector-encoding plasmid DNA into 293T cells using calcium phosphatemethod. Eighteen hours post transfection, the culture is replaced withfresh medium. Twenty-four hours post medium replacement, the supernatantcontaining the vector is collected and filtered through a 0.45 μm filterand used immediately or stored in aliquots at −80° C. for later use.Twenty micro-liter of the collected vector stocks is used to infecthuman prostate cancer cells, PC3. Twenty-four hours post infection, AZTis added to the cells to inhibit further viral replication. Forty-eighthours post infection, genomic DNA of infected PC3 cells is extracted fortiter assay. The titer of the vector stocks is determined by qPCR withan inclusion of standards of known copy numbers.

Testing of Replication Kinetics of the pAC3-yCD2-H1-shRNAmiR128Recombinant Replication Competent Retroviral Vectors in Culture.

In order to confirm that the incorporation of H1-pre-miR-128-1replicates normally, calculated volume of each vector stocks collectedfrom transient transfection mentioned above is used to infect freshhuman fibrosarcoma cells, HT1080 and human glioma cells, U87-MG,respectively, at a MOI of 0.1. Transduced cells are passaged at day 3, 6and 9 post infection. At each time point, a portion of cells arecollected for genomic DNA extraction for qPCR. Dilutions of genomic DNAare made to generate aliquots of genomic DNA with same concentration forequal amount of genomic in-put in qPCR. Replication kinetics of eachvectors are generated by plotting inversed C(t) values vs. time points.Result show that the vector replicates at similar kinetics compared tocontrol MLV virus.

Testing of Expression of Mature miR-128 from Cells Transduced with thepAC3-yCD2-H1-shRNAmiR128 Recombinant Replication Competent RetroviralVector.

To confirm the expression of miR-128 from cells transduced withpAC3-yCD2-H1-shRNAmiR128 recombinant replication competent retroviralvector, cells from day 9 post infection, at which the maximalinfectivity is reached, are expanded and harvested to extract total RNAfor detection of mature miRNA expression. Result from Taqman microRNAassay shows an over expression of mature miR-128 from both HT1080 andU87-MG cells transduced with the pAC3-yCD2-H1-shRNAmiR128 compared tountransduced cells.

Testing of Bmi-1 Expression from Cells Transduced withpAC3-yCD2-H1-shRNAmiR128 Recombinant Replication Competent RetroviralVectors to Demonstrate Target Engagement of miR-128.

Bmi-1 expression has been observed to be up-regulated in a variety ofhuman cancers including glioblastoma, and has been shown to be thetarget of miR-128. To confirm target engagement of miR-128, Bmi-1expression from cells transduced with pAC3-yCD2-H1-shRNAmiR128 isdetected by qRT-PCR. The result shows that U87-MG cells transduced withpAC3-yCD2-H1-shRNAmiR128 express lower level of Bmi-1 than untransducedcells, whereas in HT1080 cells no significant difference was observedbetween transduced and untransduced cells. The data support the conceptthat miR-128 plays an important functional role in the central nervoussystem.

Testing of yCD2 Expression from Cells Transduced withpAC3-yCD2-H1-shRNAmiR128 by Immune-Blot.

To confirm the expression of yCD2 from cells transduced withpAC3-yCD2-H1-shRNAmiR128 recombinant replication competent retroviralvector, cells from day 9 post infection, at which the maximalinfectivity is reached, are expanded and harvested to extract totalprotein for detection of yCD2 expression. The result from immune-blotshows normal expression yCD2 from both HT1080 and U87-MG cellstransduced with the pAC3-yCD2-H1-shRNAmiR128 compared to pAC3-yCD2transduced cells.

Example 13: Testing of Vector Stability of miR-128 ContainingRecombinant Retroviral Vectors in Culture

Multiple serial infection cycles of miR-128 containing recombinantretroviral vectors (pAC3-miR-128-1, pAC3-miR-128-2, pAC3-H1-shRNAmiR128and pAC3-yCD2-H1-shRNAmiR128) is tested to assess the stability of thevectors. HT1080 and U87-MG cells are initially infected with vectors ata low MOI and are allowed to spread in culture. Vector stocks at eachinfection cycles are collected, filtered diluted to infect fresh cells.At the end of each infection cycles, cells are harvested and genomic DNAare extracted for assessment of transgene stability by standard PCRusing primers that bind to the 3′ of the env gene and 3′ of theuntranslated region in the vector upstream of the 3′LTR. The resultshows that all vectors tested remain stable for at least over 8-20cycles.

Example 14: Anti-Tumor Efficacy Studies with miRNA Expressing Vector ina Mouse/Human Xenograft Model

Objective.

The objective of this study is to assess the effect of a novel MLV basedreplication-competent retroviral vectors carrying the miR128 sequence(AC3-miR128-1(V); AC3-miR128-2(V); AC3-miR128-3(V) on survival, whendelivered via intracranial (IC) injection in nude mice bearing a humanglioma xenograft, at three Toca 511 dose levels.

Mice.

Female athymic nude-Foxn1̂nu (nude) mice (age ˜8 weeks) are purchasedfrom Harlan (Indianapolis Ind.). Mice are acclimated for 7 days afterarrival. Mice undergo surgical placement of an indwelling guide cannulawith a 3.0 mm projection implanted into the right striatum, and fittedwith a cap containing a 3.5 mm projection. The stereotaxic coordinatesare AP=+0.5 mm, ML=˜1.8 mm (from bregma).

Cells.

U-87 MG cells (ATCC, Manassas Va.) are derived from a malignant gliomafrom a 44 year old Caucasian female. Cells are cultured in Dulbecco'smodified Eagles medium with 10% fetal bovine serum, sodium pyruvate, andGlutamax (Hyclone, Logan Utah, and Invitrogen, San Diego Calif.). Cellsare resuspended in PBS (Hyclone, Logan Utah) for implantation. U-87 MGcells (1E5 in 1 μL) are infused at 0.2 μL per minute (5 minutes,followed by a hold of 5 minutes) IC through an injection cannula with a3.5 mm projection inserted through the guide cannula.

Vectors preparations are made by transient transfection (or from aproducer cell line) and all have titers of approximately 5E6TU/ml. Forinitial studies vector is not further purified or concentrated. Forfollow on experiments to determine full dose response curves, high titerpurified material is prepared with a titer of around 10E8/ml. Vector isadministered IC in a volume of 5 ul or less for a minimum totaldose/mouse of approximately 2.5E4 TU/mouse.

Tumor Implantation and Vector Injection.

Six groups of female athymic nude-Foxn1̂nu mice (65 mice, 9-10 weeks ofage) are implanted IC with U-87 tumor cells (Day 0) then dosed IC (day4-7 depending on growth rate of the U87 cells) with vehicle (Groups 1),with control vector (AC3-GFP(V), Group2) or IC with AC3-miR128-1(V);AC3-miR128-2(V); AC3-miR128-3(V) (Groups 3-5). Group 6 mice were notimplanted with tumor or vector.

Data Analysis.

Survival analysis to day 60 is performed on 10 mice each from Groups 1-6and plotted as a Kaplan Meyer plot. Survival curves are compared by thelog-rank test. P values of <0.05 are considered statisticallysignificant in all analyses, which are performed with Prism 5statistical software (GraphPad Software) or equivalent.

Results from treatment with the vectors show a statistically significantsurvival advantage in this human glioma xenograft model compared totreatment with control vector or vehicle alone.

Example 15: Anti-Tumor Efficacy Studies with yCD2 and miRNA ExpressingVector in a Mouse/Human Xenograft Model

The objective of this study is to assess the effect of a novel MLV basedreplication-competent retroviral vector expressing yCD2 and miR-128,designated AC3-yCD2-H1-shRNAmiR128 (V) on survival when delivered viaintracranial (IC) injection in nude mice bearing a “stem-cell” likeenriched human glioma xenograft, at three dose levels.

Female athymic nude-Foxn1̂nu (nude) mice (age ˜8 weeks) are purchasedfrom Harlan (Indianapolis Ind.). Mice are acclimated for 7 days afterarrival. Mice undergo surgical placement of an indwelling guide cannulawith a 3.0 mm projection implanted into the right striatum, and fittedwith a cap containing a 3.5 mm projection. The stereotaxic coordinatesare AP=+0.5 mm, ML=−1.8 mm (from bregma).

Early passages of primary human glioma (Dr. Carol Kruse, BurnhamBiomedical Res Inst, San Diego, Calif.) are cultured in serum-freemedium with EGF, bFGF and B27 supplement. Cells are resuspended in PBS(Hyclone, Logan Utah) for implantation. Approximately 1000 cells in 1 μLare infused at 0.2 μL per minute (5 minutes, followed by a hold of 5minutes) IC through an injection cannula with a 3.5 mm projectioninserted through the guide cannula.

Vectors preparations are made by transient transfection (or from aproducer cell line) and all have titers of approximately 5E6TU/ml. Forinitial studies vector is not further purified or concentrated. Forfollow on experiments to determine full dose response curves, high titerpurified material is prepared with a titer of around 10E8/ml. Vector isadministered IC in a volume of 5 ul or less for a minimum totaldose/mouse of approximately 2.5E4 TU/mouse.

Tumor Implantation and Vector Injection.

Six groups of female athymic nude-Foxn1̂nu mice (66 mice, 9-10 weeks ofage) are implanted IC with “stem-like” cells (Day 0) then dosed IC atday 7-14 post tumor implantation depending on growth rate of the cellswith Groups 1: vehicle; Group2: control vector AC3-GFP(V); Group 3:TOCA511; Group 4: AC3-yH1-shRNAmiR128(V); Group 5:AC3-yCD2-H1-shRNAmiR128(V); and Group 6: untreated mice that are notimplanted with tumor or vector.

Data Analyses.

Survival analysis to day 60 is performed on 10 mice each from Groups 1-5and plotted as a Kaplan Meyer plot. Survival curves are compared by thelog-rank test. P values of <0.05 are considered statisticallysignificant in all analyses, which are performed with Prism 5statistical software (GraphPad Software) or equivalent.

Results.

Results from treatment with the vectors show a statistically significantsurvival advantage in this human glioma xenograft model compared totreatment with control vector or vehicle alone.

Example 16: Construction of Vectors with miR Target Sequences

Construction of Replication Competent Retroviral Vector Expressing GFPand Containing a Single Copy of 142-3p Target Sequence.

The replication competent retroviral vector, pAC3-emd-142-3pT, encodinga GFP was derived from the backbone of pAC3-emd described above (currentexisting patent). The pAC3-emd backbone in the pAC3-emd-142-3pT vectorwas isolated by endonuclease digestion of the pAC3-emd plasmid DNA withNot I. The perfect complementary target sequence of miR142-3pT wasobtained from published literature (Brown et al., 2006 Nature Medicine12:5 585-591). The target sequence of the miR-142-3p (SEQ ID NO: 35) wassynthesized with a Not I restriction enzyme site present at each end ofthe double-stranded DNA fragment for subsequent insertion at thecorresponding site in the pAC3-emd plasmid DNA. The orientation of the142-3pT insert was confirmed by sequencing analysis. The resultingconstruct, pAC3-emd-142-3pT, encodes 4 genes: the gag, the pol, the env,and the emd, and the non-coding 142-3pT sequence (FIG. 15).

Vector stock was produced by transient transfection of thevector-encoding plasmid DNA into 293T cells using calcium phosphatemethod. Eighteen hours post transfection, the culture was replaced withfresh medium. Twenty-four hours post medium replacement the supernatantcontaining the vector was collected and filtered through a 0.45 μmfilter and used immediately or stored in aliquots at −80° C. for lateruse. Twenty micro-liter of the collected vector stocks was used toinfect human prostate cancer cells, PC3. Twenty-four hours postinfection, AZT was added to the cells to inhibit further viralreplication. Forty-eight hours post infection, genomic DNA of infectedPC3 cells was extracted for titer assay. The titer of the vector stockswas determined by qPCR with an inclusion of standards of known copynumbers.

Construction of Replication Competent Retroviral Vector Expressing yCD2and Containing a Single Copy of 142-3p Target Sequence.

The replication competent retroviral vector, pAC3-yCD2-142-3pT, encodinga yCD2 gene was derived from the backbone of pAC3-yCD2 described above(current existing patent). The pAC3-yCD2 backbone in thepAC3-yCD2-142-3pT vector was isolated by endonuclease digestion of thepAC3-yCD2 plasmid DNA with Not I. The perfect complementary targetsequence of miR142-3pT was obtained from published literature (Brown etal., 2006 Nature Medicine 12:5 585-591). The target sequence of themiR-142-3p (SEQ ID NO: 35) was synthesized with Not I restriction enzymesite present at each end of the double-stranded DNA fragment forsubsequent insertion at the corresponding site in the pAC3-yCD2 plasmidDNA. The resulting construct, pAC3-yCD2-142-3pT, encodes 4 genes: thegag, the pol, the env, and the yCD2, and the non-coding 142-3pT sequence(FIG. 16).

Vector stock was produced by transient transfection of thevector-encoding plasmid DNA into 293T cells using calcium phosphatemethod. Eighteen hours post transfection, the culture was replaced withfresh medium. Twenty-four hours post medium replacement the supernatantcontaining the vector was collected and filtered through a 0.45 μmfilter and used immediately or stored in aliquots at −80° C. for lateruse. Twenty micro-liter of the collected vector stocks was used toinfect human prostate cancer cells, PC3. Twenty-four hours postinfection, AZT was added to the cells to inhibit further viralreplication. Forty-eight hours post infection, genomic DNA of infectedPC3 cells was extracted for titer assay. The titer of the vector stockswas determined by qPCR with an inclusion of standards of known copynumbers.

Construction of Replication Competent Retroviral Vector Expressing GFPand Containing 4 Copies of 142-3p Target Sequence.

The replication competent retroviral vector, pAC3-emd-142-3pT4X,encoding yCD2 (modified cytosine deaminase) was derived from thebackbone of pAC3-emd described above. The pAC3-yCD2 backbone in thepAC3-emd-142-3pT 4X vector was isolated by endonuclease digestion of thepAC3-emd plasmid DNA with Not I. Four tandem repeat of the perfectcomplementary target sequence of miR142-3pT4X was obtained frompublished literature (Brown et al., 2006 Nature Medicine 12:5 585-591).The target sequence of the miR-142-3p4X (SEQ ID NO: 36) was synthesizedwith a Not I restriction enzyme site present at each end of thedouble-stranded DNA fragment for subsequent insertion at thecorresponding site in the pAC3-emd plasmid DNA. The orientation of the142-3pT insert was confirmed by sequencing analysis. The resultingconstruct, pAC3-emd-142-3pT4X, encodes 4 genes: the gag, the pol, theenv, and the emd, and the non-coding 142-3pT4X sequence (FIG. 15).

Vector stock was produced by transient transfection of thevector-encoding plasmid DNA into 293T cells using calcium phosphatemethod. Eighteen hours post transfection, the culture was replaced withfresh medium. Twenty-four hours post medium replacement the supernatantcontaining the vector was collected and filtered through a 0.45 μmfilter and used immediately or stored in aliquots at −80° C. for lateruse. Twenty micro-liter of the collected vector stocks was used toinfect human prostate cancer cells, PC3. Twenty-four hours postinfection, AZT was added to the cells to inhibit further viralreplication. Forty-eight hours post infection, genomic DNA of infectedPC3 cells was extracted for titer assay. The titer of the vector stockswas determined by qPCR with an inclusion of standards of known copynumbers.

Construction of Replication Competent Retroviral Vector Expressing yCD2and Containing 4 Copies of 142-3p Target Sequence.

The replication competent retroviral vector, pAC3-yCD2-142-3pT4X,encoding a GFP was derived from the backbone of pAC3-emd describedabove. The pAC3-emd backbone in the pAC3-yCD2-142-3pT 4Xvector wasisolated by endonuclease digestion of the pAC3-yCD2 plasmid DNA with NotI. Four tandem repeat of the perfect complementary target sequence ofmiR142-3pT4X was obtained from published literature (Brown et al., 2006Nature Medicine 12:5 585-591). The target sequence of the miR-142-3pT4X(SEQ ID NO: 36) was synthesized with a Not I restriction enzyme sitepresent at each end of the double-stranded DNA fragment for subsequentinsertion at the corresponding site in the pAC3-yCD2 plasmid DNA. Theorientation of the 142-3pT4X insert was confirmed by sequencinganalysis. The resulting construct, pAC3-emd-142-3pT4X, encodes 4 genes:the gag, the pol, the env, and the emd, and the non-coding 142-3pT4Xsequence (FIG. 16).

Vector stock was produced by transient transfection of thevector-encoding plasmid DNA into 293T cells using calcium phosphatemethod. Eighteen hours post transfection, the culture was replaced withfresh medium. Twenty-four hours post medium replacement the supernatantcontaining the vector was collected and filtered through a 0.45 μmfilter and used immediately or stored in aliquots at −80° C. for lateruse. Twenty micro-liter of the collected vector stocks was used toinfect human prostate cancer cells, PC3. Twenty-four hours postinfection, AZT was added to the cells to inhibit further viralreplication. Forty-eight hours post infection, genomic DNA of infectedPC3 cells was extracted for titer assay. The titer of the vector stockswas determined by qPCR with an inclusion of standards of known copynumbers.

Example 17: Testing of Replication Kinetics

142-3pT Containing Recombinant Retroviral Vectors in Non-HematopoieticHuman Cell Lines.

In order to confirm that the incorporation of the 142-3pT sequence in avector of the disclosure replicates similar to their parental vectors,calculated volume of each vector stocks collected from transienttransfection mentioned above was used to infect fresh human fibrosarcomacells, HT1080 and human glioma cells, U87-MG, respectively, at a MOI of0.1. Transduced cells were passaged at day 3, 6 and 9 post infection. Ateach time point, a portion of cells were collected for genomic DNAextraction for qPCR. Dilutions of genomic DNA were made to generatealiquots of genomic DNA with same concentration for equal amount ofgenomic in-put in qPCR.

Replication kinetics of each vectors were generated by plotting inversedC(t) values vs. time points. FIGS. 17A and 18A show that all vectorstested replicated at similar kinetics compared to their parental vectors(pAC3-emd and pAC3-yCD2). Replication kinetics of vectors expressing GFPprotein (pAC3-emd, pAC3-emd-142-3pT and pAC3-emd-142-3pT4X) was alsoassessed by flow cytometric analysis. FIGS. 17 and 18 show thatpAC3-emd-142-3pT and pAC3-emd-142-3pT4X vectors replicated at a similarkinetic as their parental vector, pAC3-emd in these cell lines.

Testing of Replication Kinetics of 142-3pT Containing RecombinantRetroviral Vectors in Human and Mouse Hematopoietic Cells.

The expression of mature miR-142-3p was first confirmed in a mouseT-lymphocytic cell line EL4, a human T-lymphocytic cell line SUP-T1 anda human monocytic cell line U937 by Taqman microRNA assay using theprimer set specific for mouse and human miR-142-3p as the sequences ofmature miR-142-3p of the two species are identical. The replicationkinetics of recombinant retroviral vector expressing the GFP (pAC3-emd)was tested in all three cell lines with an initial infection at a MOI of2. FIG. 19 shows that the pAC3-emd vector replicated efficiently inhuman T-lymphocytes and monocytes (SUP-T1 and U937) as the viral spreadreached 65% and 95% of cell population, respectively, by day 28 postinfection. Vector spread in EL4 cells remained less than 5% during thetime frame tested in FIG. 19, but eventually spread to 40% of cells byday 60 and 70% by day 75 was observed (FIG. 20D).

Example 18: Testing of Vector Spread of 142-3pT Containing RecombinantRetroviral Vectors in Human and Mouse Hematopoietic Cells

The functional effect of miR-142-3p in suppressing the GFP expression inthe recombinant retroviral vector expressing GFP was tested by flowcytometric analysis. Calculated volume of pAC3-emd, pAC3-emd-142-3pT andpAC3-emd-142-3pT4X vector stock collected from transient transfectionmentioned above was used to infect fresh EL4, SUP-T1 and U937 cells at aMOI of 2. A portion of cells were collected at day 6, 12 and 18 postinfection for analysis of GFP expression by flow cytometric analysis.FIG. 20A shows the GFP expression was suppressed to background level inEL4 cells transduced with pAC3-emd-142-3pT and pAC3-emd-142-3pT4X vectorcompared to their parental vector pAC3-emd. The GFP suppression remainedpersistent within the time frame tested. FIG. 20B and FIG. 20C showremarkable suppression of GFP expression in SUP-T1 and U937 cellstransduced with pAC3-emd-142-3pT and pAC3-emd-142-3pT4X vector,respectively, compared to their parental vector pAC3-emd. FIG. 20D showsthat even when time is allowed for spread of the pAC3-emd vector toapproximately 30% at 55 days, expression of pAC3-emd-142-3pT andpAC3-emd-142-3pT4X vector continues to be suppressed. The resultsconfirm that the miR-142-3p expression in mouse and human hematopoieticcells effectively suppress the GFP expression in cells transduced withrecombinant retroviral vectors containing the 142-3pT sequence. In U937cells, the result suggested that the vector containing 4 copies of142-3pT (pAC3-emd-142-3pT4X) may be more effective in suppressing GFPexpression than the vector containing single copy of 142-3pT(pAC3-emd-142-3pT4X).

Example 19: Testing of Viral RNA Genome

It is unclear whether the functional effect of miR-142-3pT insuppressing the GFP expression mentioned above is due direct suppressionof GFP expression at the translational level or due to degradation ofviral genome at post transcriptional level. A portion of cells at theend of the experimental time point is collected for total RNA extractionusing standard molecular biology method. qRT-PCR using primers (e.g. polprimer set and env2 primer set) specific to cDNA derived from reversetranscribed viral RNA is performed to assess viral load of transducedcells. The result shows that the viral load of cells transduced withpAC3-emd-142-3pT and pAC3-emd-142-3pT4X, respectively, is significantlylower than cells transduced with pAC3-emd vector. The result supportsthe concept that miR-142-3p in mouse and human hematopoietic cellseffectively degrades the viral RNA genome at post transcriptional level,thereby, restricts the vector spread in mouse and human hematopoieticcells.

Example 20: Testing of Integrated Proviral DNA by qPCR

It is unclear whether the functional effect of miR-142-3pT insuppressing the GFP expression mentioned above is due direct suppressionof GFP expression at the translational level or due to degradation ofviral genome and thus integration of proviral DNA. A portion of cells atthe end of the experimental time point is collected for genomic DNAextraction using standard molecular biology methods. qPCR using primersspecific to integrated proviral DNA is performed to assess the copynumber of integrated proviral DNA per cell. The result shows that thecopy number per cells of cells transduced with pAC3-emd-142-3pT andpAC3-emd-142-3pT4X, respectively, is significantly lower than cellstransduced with pAC3-emd vector. The result supports the concept thatmiR-142-3p in mouse and human hematopoietic cells effectively degradesthe viral RNA genome at post transcriptional level, and therebyrestricts the vector spread in mouse and human hematopoietic cells.

Example 21: Testing of Vector Stability of 142-3pT ContainingRecombinant Retroviral Vectors in Culture

Multiple serial infection cycles of 142-3pT containing recombinantretroviral vectors is tested to assess the stability of the vectors.HT1080 and U87-MG cells are initially infected with vectors at a low MOIand are allowed to spread in culture. Vector stocks at each infectioncycles are collected, filtered and diluted to infect fresh cells. At theend of each infection cycles, cells are harvested and genomic DNA areextracted for assessment of transgene stability by standard PCR usingprimers that bind to the 3′ of the env gene and 3′ of the untranslatedregion in the vector downstream of the heterologous polynucleotidesequence linked to the IRES. The result shows that vectors containingsingle copy of 142-3pT (pAC3-emd-142-3pT and pAC3-yCD2-142-3pT) remainsstable for at least over 10-20 cycles, whereas vectors containing 4tandem repeats of 142-3pT (pAC3-emd-142-3pT4X and pAC3-yCD2-142-3pT4X)can show deletion of 142-3pT sequence in early infection cycles.

Example 22: Testing of Controlled Vector Spread of 142-3pT ContainingRecombinant Retroviral Vectors in In Vivo

This experiment is conducted with the same design as example 27 below.The functional effect of miR-142-3p in restricting vector spread viahematopoietic cells is tested in vivo by intravenous injection of therecombinant retroviral vectors (pAC3-emd, pAC3-emd-142-3pT andpAC3-emd-142-3pT4X) in 8-wk-old nude Balb/C mice with implanted U87xenografts. For each vector, there are three groups of mice eachrepresents a time point (e.g. 30 day, 60 day and 90 day post viralvector administration). A dose of 1E4 to 1E7 TU of each vector stock isadministered by intravenous injection to all animals. Animals from eachtime point are sacrificed to harvest spleen, lymph nodes and bone marrowand tumor. GFP expression of subpopulation of cells (e.g. CD4+, CD8+ andetc.) are harvested and analyzed by flow cytometric analysis. In aduplicate experiment, animals from each time point are sacrificed andtissues (e.g. liver, kidney, spleen, tumor etc.) are collected forgenomic DNA extraction. qPCR is performed to assess the presence ofintegrated proviral DNA in tissues collected. The result shows vectorspread of vectors containing the 142-3pT is significantly reduced inhematopoietic tissues demonstrating the reduction of vector replicationin these tissues. At the same time GFP and PCR signal is still observedin the tumor, showing that the miR target sequences have depressedspread in the lymphoid tissues, but still allowed spread in the tumortissue.

Example 23. Extended Survival in a Patient Dog with SpontaneousRecurrent Malignant Glioma and Treated with T5.0002 Vector Plus 5-FC

A male 35 kg Boxer dog, presenting with recurrent anaplasticoligodendroglioma 3 months following complete surgical resection, wastreated with T5.0002 virus, purified and formulated (see U.S. Pat. No.5,792,643; T. Rodriugez et al. J Gene Med 9:233 2007; WO 2010/148203) inisotonic Tris/NaCl pH7.2 rendered isotonic with mannitol & sucrose, 1mg/ml HSA, 0.1 mg/ml ascorbate) in combination with 5-FC. The tumormeasured approximately 13 cm³, and caused major lateral ventriclecompression and significant midline shift (See FIG. 1) Due to the largesize of the tumor, Toca 511 was infused through 2 separate catheters(400 μL and 480 μL), using Convection Enhanced Delivery (CED). The totalToca 511 dose administered was approximately 4.1×10⁶ TU/g brain.ProHance® (gadoteridol) was added to Toca 511 prior to injection toallow visualization of delivery by MRI. The volume of distribution ofthe vector was estimated to be approximately 10-12% of the tumor volume.

FIGS. 21 A and 21B are still frames from the MRI images obtained fromthe patient dog during intratumoral CED infusion of Toca 511 andgadolinium. Note the large tumor on the left side of the imagecompressing both sides of the brain and shifting midline structures tothe right. The white areas are the gadolinium-Toca 511 infusion. FIG.21B shows the placement of the two catheters into the tumor.

Toca 511 was allowed to spread for 8 days. The dog was treated with 5-FCat a divided dose of 130 mg/kg/day, by mouth, three times daily withfood for 5 days. The dose was increased to 160 mg/kg/day for 2 more days(7 days of 5-FC total). A follow-up MRI showed no change in tumor sizeand some possible changes to the internal area of the tumor. After 21days of viral spread, a second cycle of 5-FC was initiated at the higherdose of 160 mg/kg/day (divided, three times a day with food). The drugwas stopped after the fifth day of dosing due to the development ofrash.

MRI performed at 2 weeks after the first course of 5-FC and 2 weeksafter the second course of 5-FC (7 weeks after treatment began) hasshown that the tumor volume has plateaued while the rate of tumor growthhas declined. The patient became more alert and active, and remainedclinically stable, 13 weeks after injection of vector. At 15.5 weeks thedog was euthanized because of stomach bleeding due to prolonged highdose steroid administration (and not because of the tumor). Theestimated lifespan of the dog was no more than 3-4 weeks at the time ofinitial injection of the vector. Efficacy of the Toca 511/5-FCcombination in this patient dog is shown by survival 3 to 4 times longerthan that originally estimated by his attending veterinarian. At autopsylow levels (20-30 copies/microgram genomic DNA) of vector DNA weredetectable in the residual tumor, but nowhere else in the dog.

Example 24 Construction of Gamma Interferon Vectors

Construction and Testing of a Replication Competent Retroviral VectorEncoding the Human IFN-Gamma Gene.

The replication competent retroviral vector, pAC3-hIFNg, encoding thehuman IFN-gamma gene, was derived from the backbone of pAC3-yCD2described above. The pAC3 backbone in the pAC3-hIFNg vector was isolatedby endonuclease digestion of the pAC3-yCD2 plasmid DNA with Psi I andNot I. The cDNA sequence of human IFN-gamma gene was identified andconfirmed among three sequences obtained from different accessionnumbers (AM903379, BC070256, and NM000619). Sequence alignment showedidentical sequence among the three. The open reading frame of the humanIFN-gamma (SEQ ID NO: 38) was synthesized with Psi I and Not Irestriction enzyme site present at each end of the DNA fragment forsubsequent insertion at the corresponding site in the pAC3 backbone. Theresulting construct, pAC3-hIFNg, encodes 4 genes: the gag, the pol, theenv, and the human IFN-gamma (FIG. 22).

Vector stock was produced by transient transfection of thevector-encoding plasmid DNA into HT1080 cells using FUGENE HDtransfection Reagent. Forty-eight hours post transfection thesupernatant containing the vector was collected and filtered through a0.45 μm filter and used immediately or stored in aliquots at −80° C. forlater use. Specific volume of the undiluted vector stock was used toinfect fresh 75% confluent HT1080. At day 4 and day 5 post infection,the supernatant containing the vector was collected and filtered througha 0.45 μm filter and used immediately or stored in aliquots at −80° C.for later use. Twenty micro-liter of the collected vector stocks wasused to infect human prostate cancer cells, PC3. Twenty-four hours postinfection, AZT was added to the cells to inhibit further viralreplication. Forty-eight hours post infection, genomic DNA of infectedPC3 cells was extracted for titer assay. The titer of the vector stockswas determined by qPCR with an inclusion of standards of known copynumbers.

The expression of human IFN-gamma was first tested at the RNA level.Total RNA was extracted from transduced HT1080 cells at 5 days postinfection in the second infection using standard RNA extraction method.RT-PCR was performed to detect the expression of human IFN-γ. Fiftynano-gram of total RNA was used in the RT reaction to generate cDNA. Onetenth of the volume from RT reaction was subsequently used for PCR usingPCR primer set specific for human IFN-γ. Result from RT-PCR showed thathuman IFN-gamma is expressed in HT1080 cells infected with pAC3-hIFNgvector.

The expression of secreted human IFN-□ protein was tested by standardELISA. Vector stock collected from day 4 and day 5 post infection wasserially diluted in the ELISA assay in order to obtain a linear rangebetween protein concentration and dilution factor. The result showedthat human IFN-γ protein is secreted at a higher concentration by theHT1080 cells at day 5 post infection than by the cells at day 4 postinfection (FIG. 24). Cells at post d5 infection secreted approximately325-355 pg/mL human IFN-γ protein.

Construction and Testing of a Replication Competent Retroviral VectorEncoding the Mouse IFN-Gamma Gene.

The replication competent retroviral vector, pAC3-mIFNg, encoding themouse IFN-γ gene was derived from the backbone of pAC3-yCD2 describedabove. The pAC3 backbone in the pAC3-mIFNg vector was isolated byendonuclease digestion of the pAC3-yCD2 plasmid DNA with Psi I and NotI. The cDNA sequence of mouse IFN-γ gene was identified and confirmedamong three sequences obtained from different accession numbers(BC119063, BC119065 and NM008337). Sequence alignment showed identicalsequence among the three. The open reading frame of the mouse IFN-gamma(SEQ ID NO: 39) was synthesized with Psi I and Not I restriction enzymesite present at each end of the DNA fragment for insertion at thecorresponding site in the pAC3 backbone. The resulting construct,pAC3-mIFNg, encodes 4 genes: the gag, the pol, the env, and the mouseIFN-gamma (FIG. 22).

Vector stock was produced by transient transfection of thevector-encoding plasmid DNA into HT1080 cells using FUGENE HDtransfection Reagent. Forty-eight hours post transfection thesupernatant containing the vector was collected and filtered through a0.45 micron filter and used immediately or stored in aliquots at −80° C.for later use. Specific volume of the undiluted vector stock was used toinfect fresh 75% confluent HT1080. At day 4 and day 5 post infection thesupernatant containing the vector was collected and filtered through a0.45 micron filter and used immediately or stored in aliquots at −80° C.for later use. Twenty micro-liter of the collected vector stocks wasused to infect human prostate cancer cells, PC3. Twenty-four hours postinfection, AZT was added to the cells to inhibit further viralreplication. Forty-eight hours post infection, genomic DNA of infectedPC3 cells was extracted for titer assay. The titer of the vector stockswas determined by qPCR with an inclusion of standards of known copynumbers.

The expression of mouse IFN-gamma was first tested at the RNA level.Total RNA was extracted from transduced HT1080 cells at 5 days postinfection in the second infection using standard RNA extraction method.RT-PCR was performed to detect the expression of mouse IFN-gamma. Fiftynano-gram of total RNA was used in the RT reaction to generate cDNA. Onetenth of the volume from RT reaction was subsequently used for PCR usingPCR primer set specific for mouse IFN-gamma (FIG. 23). Result fromRT-PCR showed that mouse IFN-gamma is expressed in HT1080 cells infectedwith pAC3-mIFNg vector.

The expression of secreted human IFN-gamma protein was tested bystandard ELISA. Vector stock collected from day 4 and day 5 postinfection was serially diluted in the ELISA assay in order to obtain alinear range between protein concentration and dilution factor. Theresult showed that mouse IFN-γ protein is secreted at a higherconcentration by the HT1080 cells at day 5 post infection than by thecells at day 4 post infection (FIG. 25). Cells at post d5 infectionsecreted approximately 33-42 ng/mL mouse IFN-gamma protein.

Example 25: Anti-Tumor Efficacy Studies with Gamma Interferon ExpressingVector in a Mouse Subcutaneous Tumor Model

Objective.

The objective of this study is to assess the effect of a novel MLV basedreplication-competent retroviral vector carrying the murine gammainterferon sequence (pAC3-mIFNg) on tumor growth, when delivered viaintratumoral (IT) injection in BALB/c mice bearing subcutaneous coloncarcinoma (CT26.WT).

Mice.

Female BALB/c mice (age ˜8 weeks) are purchased from JacksonLaboratories (Bar Harbor, Me.). Mice will be acclimated for 7 days afterarrival before start of studies.

Cells.

CT26.WT cells (ATCC, Manassas Va.) are anN-nitroso-N-methylurethane-(NNMU) induced, undifferentiated coloncarcinoma cell line. Cells are cultured in Dulbecco's modified Eaglesmedium with 10% fetal bovine serum, sodium pyruvate, and Glutamax(Hyclone, Logan Utah, and Invitrogen, San Diego Calif.). Cells areresuspended in PBS (Hyclone, Logan Utah) for implantation. CT26.WT cells(2E5 in 100 μL) are injected into the right flank of BALB/c mice.

Vectors.

Vectors preparations are made by transient transfection (or from aproducer cell line after infection of a second cell line with theinfectious virus from the initial transfection; see, e.g., InternationalApplication No. PCT/US10/38996, the disclosure of which is incorporatedherein by reference) with titers of approximately 3×10⁶TU/ml. Forinitial studies vector is not further purified or concentrated. Forfollow on experiments to determine full dose response curves, high titerpurified material is prepared with a titer expected around 10⁸/ml. Toachieve high titer material, canine cell line CF2 are chosen forproduction as gamma interferon is poorly cross-species reactive and useof xenogeneic cell lines will prevent the inhibitory action of gammainterferon on the producing cells. The vector is purified andconcentrated as described in the specification (see also T. Rodriguez etal. J Gene Med 9:233 2007). Vector is administered IT in a volume of 100μL and the total dose/mouse of approximately 3E3, 3E4 and 3E5 TU/mouse.Vector expressing gamma interferon is identified as Toca 621.

Tumor Implantation and Vector Injection.

Nine groups of female BALB/c (99 mice, 9-10 weeks of age) are implantedsubcutaneously with CT26.WT tumor cells (Day 0) and then dosed (day 4-7depending on growth rate of the CT26 tumor; approximately 50-100 mm³)with vehicle (Groups 1), with control vector [AC3-GFP(V), (Group2), ITToca 621 vector injection (Groups 3-5), or intravenous Toca 621 vectorinjection (group 6-8). Group 9 mice have no tumor implanted and areintravenously injected with vector only.

Data Analysis.

Tumor growth analysis is carried out to 2000 mm³ or to 60 days based onwhichever comes first. 10 mice from each group will be plotted for tumorsize over time. Statistical significance are determined using analysisof variance (ANOVA). P values of <0.05 are considered statisticallysignificant in all analyses, which are performed with Prism 5statistical software (GraphPad Software) or equivalent. In-lifeobservations are also taken to assess any adverse events to Toca 621administration.

Results.

The results of measurement of tumor size over time show a statisticallysignificant difference in the growth of tumors treated with the vectorexpressing gamma IFN over the tumors in animals that received controlvector or vehicle.

Example 26 Anti-Tumor Efficacy Studies with Gamma Interferon ExpressingVector in a Mouse Subcutaneous Tumor Model

Objective.

The objective of this study was to assess the effect of a novel MLVbased replication-competent retroviral vector carrying the murine gammainterferon sequence (pAC3-mIFNg) on tumor growth, when delivered viaintratumoral (IT) injection in BALB/c mice bearing subcutaneous melanoma(Cloudman S91).

Mice.

Female BALB/c mice (age ˜8 weeks) were purchased from JacksonLaboratories (Bar Harbor, Me.). Mice were acclimated for 7 days afterarrival before start of studies.

Cells.

Clone M-3 Cloudman S91 cells (ATCC, Manassas Va.) are derived from anirradiation induced malignant melanoma from a C x DBA F1 mouse. Cellswere cultured in Dulbecco's modified Eagles medium with 10% fetal bovineserum, sodium pyruvate, and Glutamax (Hyclone, Logan Utah, andInvitrogen, San Diego Calif.). Cells were resuspended in PBS (Hyclone,Logan Utah) for implantation. S91 cells (1E5 in 100 μL) were injectedinto the right flank of BALB/c mice.

Vectors.

Vectors preparations are made by transient transfection (or from aproducer cell line after infection of a second cell line with theinfectious virus from the initial transfection with titers ofapproximately 3E6TU/ml. For initial studies vector was not furtherpurified or concentrated. For follow on experiments to determine fulldose response curves, high titer purified material was prepared with atiter approximately 10̂8 TU/ml. To achieve high titer material, the humancell line HT1080 was used for production of the mouse gamma interferonvector as gamma interferon is poorly cross-species reactive and use ofxenogeneic cell lines prevents the inhibitory action of gamma interferonon the producing cells. The vector was purified and concentrated asdescribed in the specification above. Vector was administered IT in avolume of 100 μL and the total dose/mouse of approximately 3E3, 3E4 and3E5 TU/mouse. Vector expressing gamma interferon is identified as Toca621.

Tumor Implantation and Vector Injection.

Two groups of female BALB/c (approx. 20 mice, 9-10 weeks of age) wereimplanted subcutaneously with S91 tumor cells. Mice with tumors reachingapproximately 50-125 mm3 were randomized and injected IT with controlvector, Toca 511 (Groups 1, N=10), or Toca 621 vector (Group 2, N=5).

Data Analyses.

Tumor growth analysis was carried out to 600 mm3 or to 45 days based onwhichever comes first. All mice from each group were plotted for tumorsize over time. Statistical significance was determined using analysisof variance (ANOVA). P values of <0.05 are considered statisticallysignificant in all analyses, which are performed with Prism 5statistical software (GraphPad Software) or equivalent. In-lifeobservations were also taken to assess any adverse events to Toca 621administration.

Results.

A statistically significant reduction in average tumor volume wasmeasured in mice with tumors injected with a single dose of Toca 621vector expressing gamma IFN compared to mice with tumors injected withcontrol Toca 511 vector (p=0.003) see FIG. 35.

Example 27 Intravenous Gene Delivery Using a Replicative RetroviralVector

Objective.

The objective of this study was to assess the effectiveness ofintravenous delivery of a novel MLV based replication-competentretroviral vector carrying the marker green fluorescent protein(AC3-GFP(V)) to U87 gliomas implanted in the brains of nude mice.

Mice.

Female athymic nude-Foxn1̂nu (nude) mice (age ˜8 weeks) were purchasedfrom Harlan (Indianapolis Ind.). Mice were acclimated for 7 days afterarrival. Mice underwent surgical placement of an indwelling guidecannula with a 3.0 mm projection implanted into the right striatum, andfitted with a cap containing a 3.5 mm projection. The stereotaxiccoordinates are AP=+0.5 mm, ML=−1.8 mm (from bregma).

Cells.

U-87 MG cells (ATCC, Manassas Va.) are derived from a malignant gliomafrom a 44 year old Caucasian female. Cells were cultured in Dulbecco'smodified Eagles medium with 10% fetal bovine serum, sodium pyruvate, andGlutamax (Hyclone, Logan Utah, and Invitrogen, San Diego Calif.). Cellsare resuspended in PBS (Hyclone, Logan Utah) for implantation. U-87 MGcells (1E5 in 1 μL) were infused at 0.2 μL per minute (5 minutes,followed by a hold of 5 minutes) intracranially (IC) through aninjection cannula with a 3.5 mm projection inserted through the guidecannula.

Vectors.

Vector preparations were made by transient transfection and all had atiter of approximately 2.8E7TU/ml. Vector was administeredintratumorally (IT) in a volume of 5 ul or less for a minimum totaldose/mouse of approximately 1.4E45 TU/mouse. Intravenous injections weredone through the tail vein with 2.8E6/100 uL.

Tumor Implantation and Vector Injection.

Five groups of female athymic nude-Foxn1̂nu mice (16 mice, 9-10 weeks ofage) were implanted IC with U-87 tumor cells (Day 0) then dosed IT or IV(day 4-7 depending on growth rate of the U87 cells) with vehicle IV(Group 1), with vector IV (Group2), IT with a blood/brain barrierdisruptor Vardenafil and vector (Group 3), IT with Vardenafil and vector(Groups 4), or IT with vector (group 5). 14 days after vector injectionmice were sacrificed and tumors are isolated and analyzed for GFPexpression.

Data Analysis.

U87 cells from disrupted tumors isolated from the mice were analyzed byflow cytometry for the percentage GFP positive from groups 2-5 (FIG.26). Histogram analysis was also done on groups 1, 3, and 5 to measurethe distribution of GFP signal in isolated U87 cells (FIG. 27).

Results.

Intravenous delivery of GFP was as equally effective as intratumorinjection of U87 glioma cells intracranially implanted into nude mice.

Example 28 Construction of Replication Competent Retroviral VectorEncoding the Human IL-2 Gene

The replication competent retroviral vector, pAC3-hIL2, encoding thehuman IL2 gene, is derived from the backbone of pAC3-yCD2 vector. ThepAC3 backbone in the pAC3-hIL2 vector-encoding plasmid DNA was isolatedby endonuclease digestion of the pAC3-yCD2 plasmid DNA with Psi I andNot I. The cDNA sequence of human IFN-γ gene was identified andconfirmed using sequences obtained from different accession numbers(BC066255 and BC066257). Sequence alignment of the two revealedidentical sequence. The open reading frame of the human IFN-γ (SEQ IDNO: 40) was synthesized with Psi I and Not I restriction enzyme sitepresent at each end of the DNA fragment for subsequent insertion at thecorresponding site in the pAC3 backbone. The resulting construct,pAC3-hIL2, encodes 4 genes: the gag, the pol, the env, and the humanIL2. (FIG. 28).

Vector stock is produced by transient transfection of thevector-encoding plasmid DNA into 293T cells using calcium phosphatemethod. Eighteen hours post transfection, the culture was replaced withfresh medium. Twenty-four hours post medium replacement, the supernatantcontaining the vector was collected and filtered through a 0.45 μmfilter and used immediately or stored in aliquots at −80° C. for lateruse. Twenty micro-liter of the collected vector stocks was used toinfect human prostate cancer cells, PC3. Twenty-four hours postinfection, AZT was added to the cells to inhibit further viralreplication. Forty-eight hours post infection, genomic DNA of infectedPC3 cells was extracted for titer assay. The titer of the vector stockswas determined by qPCR with an inclusion of standards of known copynumbers.

The expression of human IL-2 is first tested at the RNA level. Total RNAis extracted from transduced CF2TH and HT1080 cells at 5 days postinfection using standard RNA extraction method. RT-PCR was performed todetect the expression of human IL-2. Fifty nano-gram of total RNA wasused in the RT reaction to generate cDNA. One tenth of the volume fromRT reaction was subsequently used for PCR using PCR primer set specificfor human IL-2. Result from RT-PCR shows that human IL-2 is expressed inHT1080 cells transduced with pAC3-hIL2 vector.

The expression of secreted human IL-2 protein was tested by standardELISA. Vector stock collected from day 5 post infection was seriallydiluted in the ELISA assay in order to obtain a linear range betweenprotein concentration and dilution factor. The result showed that humanIL-2 protein is secreted at a higher concentration by the CF2TH cellsthan HT1080 at day 5 post infection.

Example 29 Anti-Tumor Efficacy Studies with Interleukin 2 ExpressingVector in a Mouse Subcutaneous Tumor Model

Objective.

The objective of this study is to assess the effect of a novel MLV basedreplication-competent retroviral vector carrying the murineleukocytotrophic hormone interleukin 2 (IL-2) sequence (pAC3-mIL2) ontumor growth, when delivered via intratumoral (IT) injection in BALB/cmice bearing subcutaneous colon carcinoma (CT26.WT).

Mice.

Female BALB/c mice (age ˜8 weeks) are purchased from JacksonLaboratories (Bar Harbor, Me.). Mice will be acclimated for 7 days afterarrival before start of studies.

Cells.

CT26.WT cells (ATCC, Manassas Va.) are anN-nitroso-N-methylurethane-(NNMU) induced, undifferentiated coloncarcinoma cell line. Cells are cultured in Dulbecco's modified Eaglesmedium with 10% fetal bovine serum, sodium pyruvate, and Glutamax(Hyclone, Logan Utah, and Invitrogen, San Diego Calif.). Cells areresuspended in PBS (Hyclone, Logan Utah) for implantation. CT26.WT cells(2E5 in 100 μL) are injected into the right flank of BALB/c mice.

Vectors.

Vector preparations are made by transient transfection (or from aproducer cell line) with titers of approximately 6E6TU/ml. For initialstudies vector is not further purified or concentrated. For follow onexperiments to determine full dose response curves, high titer purifiedmaterial is prepared with a titer expected around 10E8/ml. Vector isadministered IT in a volume of 100 μL and the total dose/mouse ofapproximately 6E5 TU/mouse. Vector expressing gamma interferon isidentified as Toca IL2.

Tumor Implantation and Vector Injection.

Five groups of female BALB/c (55 mice, 9-10 weeks of age) are implantedsubcutaneously with CT26.WT tumor cells (Day 0) and then dosed (day 4-7depending on growth rate of the CT26 tumor; approximately 50-100 mm³)with vehicle (Groups 1), with control vector [AC3-GFP(V), (Group2), ITToca IL2 vector injection (Groups 3), or intravenous Toca IL2 vectorinjection (group 4). Group 5 mice have no tumor implanted and areintravenously injected with vector only.

Data Analysis.

Tumor growth analysis is carried out to 2000 mm³ or to 60 days based onwhichever comes first. 10 mice from each group will be plotted for tumorsize over time. Statistical significance will be determined usinganalysis of variance (ANOVA). P values of <0.05 are consideredstatistically significant in all analyses, which are performed withPrism 5 statistical software (GraphPad Software) or equivalent. In-lifeobservations are also taken to assess any adverse events to IL-2expression during treatment.

Results.

Delivery of IL-2 by replicating MLV reduces and in some instances clearstumors burden from the BALB/c CT26 mouse model.

Example 30 Tumor Explants have Multiple Copies of the Vector Genome andShow Continued Susceptibility to Super-Infection

In order to examine in more detail the mechanism of action of thereplicating retrovirus tumors from some animals in the mouse and humantumor models described in example 9 (athymic nude-Foxn1̂nu (nude) micewith Human U87 intracranial implants) and example 10 (BALB/c mice withsyngeneic CT26 intracranial implants) were explanted and examined for5-FC sensitivity, vector copy number/diploid genome, and CD proteinexpression.

Explant Assignments.

The experimental design is summarized below. The study consisted of 5tumor explants. The history of each tumor removed for implantation isgiven below.

Explant History:

# of 5-FC dosings Ani- before Cell Dosing mal # Study Treatment explantType regimen 833 Example 9 AC3-yCD2(V) 4 Human QD, 7 days FIG. 8 E6 +5-FC U87 every 21 days 953 Example 9 AC3-yCD2(V) 4 Human QD, 7 days FIG.8 E5 + 5-FC U87 every 21 days 969 Example 9 AC3-yCD2(V) 4 Human QD, 7days FIG. 8 E5 + 5-FC U87 every 21 days 31 Example 10 AC3-yCD2(V) 3.5Mouse BID 7 days, FIG. 9 E5 + 5-FC CT26 every 17 days 61 Example 10AC3-yCD2(V) 3 Mouse BID 7 days, FIG. 9 E4 + 5-FC CT26 every 17 days

The 5-FC cell killing assays were carried out as described in Example 5above, measuring viability after 8 days of 5-FC treatment.

Copy number/microgram of DNA was determined by PCR as described for thevector tittering assay in Example 5, and converted to copynumber/diploid genome by dividing by 150,000, the approximate number ofdiploid mouse/human genomes in 1 microgram of genomic DNA. Western Blotanalysis was performed on 1E6 cells/lysate in RIPA buffer usingantibodies from clone 83A25 for GP70 and Abcam anti-CD antibody ab3525for the CD protein. Cell explants underwent super-infection procedureswith a AC3-eGFP(V) and a mock procedure to determine which explants werepotentially further infectable. The extent of GFP expression wasmeasured by FACS analyses, with uptake and expression of GFP indicatingthe relative susceptibility to further infection.

Results. 5-FC Cell Killing Assay and Copy Number of Integrated Vector.

Cultured explants were tested for 5-FC sensitivity by generating akilling profile from treated cell lines at varying 5-FC concentrations(summarized in the Table below). Results from the killing profilemeasured by MTS viability assay show that U87 human tumors derived fromanimals #833, 953, 969 on average (IC₅₀=0.009 mM) had a similar responsecompared to an in vitro U87 positive control (IC₅₀=0.008 mM) to 5-FCtreatment (FIG. 29A). Analysis of CT26 murine tumors (Example 10) showedthat the 5-FC responsive animal #61 had an IC₅₀ of 0.003 mM (FIG. 29B)which is similar to in vitro 100% transduced CT26 results (IC₅₀=0.001mM). Animal #31 was poorly responsive to 5-FC (FIG. 29B). PCR resultsfor copy number per cell are also shown in the table below.

5-FC sensitivity Vector copy number Animal # Study IC50 (mM) per diploidgenome 833 Example 9 0.009 22.3 953 Example 9 0.009 9.6 969 Example 90.009 18.7 61 Example 10 0.003 6.0 31 Example 10 Not sensitive 0.9

Western Blot Analysis of GP70 and CD Protein Expression.

Further analysis of cells by western blot from the CT26 study showedthat both tumor explants derived from mice #31 and #61 had observableGP70 protein expression when using U87+AC3-yCD2(V) infected lysates as areference positive control (FIG. 30).

However, analysis of CD expression showed that only #61 still hadobservable CD expression. Cells from #31 were run in duplicate wells(#31(A) and #31(B)) to verify negative CD gene expression results.

GFP Expression after AC3-eGFP(V) Transduction.

Attempts to transduce explants with an MLV vector expressing GFP showedthat U87 tumors derived from animals #833, 953, 969 were scarcelytransducible (<0.5%). CT26 explanted tumor cells derived from animal #61could be partially transduced (7% GFP positive) while explanted cellsfrom animal #31 could not (FIG. 31).

All U87 gliomas isolated from the brains of nude mice after 4 fullcycles of 5-FC treatment were still sensitive to 5-FC treatment in vitrowith an IC₅₀ the same as in vitro transduced U87 and, surprisingly,showed multiple vector superinfections had taken place. Two CT26 tumorswere isolated from BALB/c mice after 3 and 3.5 cycles of 5-FC treatment.Of the two, only one tumor showed 5-FC sensitivity while the other didnot. Further analysis showed that the 5-FC resistant tumor is refractoryto further MLV transduction, expresses GP70 but no longer expresses theCD, and has low copy number compared to the other CT26 and all U87explants tested. These observations show that whereas a virus that hasundergone a deletion of the CD gene behaves as expected for a normalretrovirus and excludes further infection, cells infected with vectorcarrying the CD transgene behave atypically and allow multiplesuperinfections (range: 6.0-23.3, mean 14.5 copies per diploid genome).Typical tumors are not diploid but are polyploid with a genome largerthan the diploid genome. This would further increase the actual vectorcopy number per cell. The multiple vector copy numbers contributes tothe therapeutic effect as more of the protein derived from the transgene(in this case CD) is produced than from a single vector integration. Italso means that in general, even if some members of a viral vectorpopulation undergo rearrangements, other members will donate proteinactivity (in this case sensitivity to 5-FC). The experiments describedhere also provide a method of testing a recombinant replicationcompetent retrovirus for the property of multiple infections of a targetcell population.

Example 31: Direct Measurement from Excised Tumors Treated withAC3-yCD2(V) Shows Unexpectedly High Levels of Viral Vector Copies PerGenome and Susceptibility to Superinfection in the Syngeneic Tu2449Glioma Model

Objective.

This study was conducted to compare the efficacy of two dose levels ofAC3(V)-yCD2 (aka Toca511) delivered via IC injection in combination with5-FC treatment in a TU-2449 glioma tumor bearing, immunocompetent mousemodel, and examined survival in the setting of active tumor growth.TU-2449 cells implanted IC in syngeneic B6C3F1 mice have been used as anexperimental murine glioma model. This model was also used for survivaland short term (15-18 day) experiments where tumors were implanted,treated with vector and dosed short term with 5-FC then excised forfurther characterization of gene copy number and CD activity.

Mice.

Female B6C3F1 mice (age ˜8 weeks) were purchased from Harlan(Indianapolis Ind.). Mice were acclimated for 7 days after arrival.

Mice underwent surgical placement of an indwelling guide cannula with a3.0 mm projection implanted into the right striatum, and fitted with acap containing a 3.5 mm projection. The stereotaxic coordinates wereAP=+0.5 mm, ML=−1.8 mm (from bregma).

Cells.

TU-2449 cells (Smilowitz et al. J Neurosurg. 2007 106:652-659 2007)derived originally from Glial fibrillary acidic protein (GFAP)-v-srctransgenic mice, were cultured in Dulbecco's modified Eagles medium with10% fetal bovine serum, sodium pyruvate, and Glutamax (Hyclone, LoganUtah, and Invitrogen, San Diego Calif.). Cells were resuspended in PBS(Hyclone, Logan Utah) for implantation. TU-2449 cells (1E4 in 1 μL) wereinfused at 0.2 μL per minute (5 minutes, followed by a hold of 5minutes) IC through an injection cannula with a 3.5 mm projectioninserted through the guide cannula.

The study consisted of 6 groups of female mice (see Table below). On day0, mice from Groups 1, 3, 4, 6, and 7 underwent intracranialimplantation of 1E4 TU-2449 cells. Group 8 mice were not implanted withtumor. On Day 4, mice were injected (IC; 5 μL/mouse) with vehicle (Group1); IC with AC3-yCD2(V) at 1.7E5 TU/g (Groups 6, 7); IC with AC3-yCD2(V)at 1.7E6 TU/g (Groups 3, 4); Group 8 mice were not treated. Starting onDay 10, mice were treated IP BID for 4 consecutive days with PBS (Groups1, 3, 7) or 5-FC (500 mg/kg/dose, Groups 4, 6, 8). Cycles of 4 days BIDtreatment with PBS or 5-FC followed by 10 days of viral spread wererepeated. Survival analysis to Day 180 was performed on 10 mice eachfrom Groups 3-7.

Group Assignments N per analysis category Scheduled Group TreatmentSurvival Sacrifice 1 Control (vehicle 1 at day 10 injection) + PBS 3AC3-yCD2(V) 10 E6 + PBS 4 AC3-yCD2(V) 10 3 at day 10, 24, E6 + 5-FC 38,and 52 6 AC3-yCD2(V) 10 3 at day 10, 24, E5 + 5-FC 38, and 52. 7AC3-yCD2(V) 10 E5 + PBS 8 5-FC 1 at day 10, 24, (no tumor) 38, and 52TOTAL 40 29

AC3-yCD2(V) (5 μL) was infused at 0.33 μL per minute (15 minutes,followed by a hold of 5 minutes) intracranially through an injectioncannula with a 3.5 mm projection inserted through the guide cannula.5-FC (500 mg/kg/dose) or PBS (800 μL) was administered IP BID for 4consecutive days starting at days 10, 24, 38, and 52.

Short Term Experiments to Determine the Level of Viral Genome andSuper-Infection in Tu2449 Tumors In Vivo.

The study consisted of 6 groups of female mice (see Table below). Allgroups underwent intracranial administration into the right striatum of1E4 TU-2449 cells administered/mouse on Day 0. At Day 4, all groupsreceived intracranial/intratumoral administration of AC3-YCD2(V) vectorat 2.4E6 TU/5 ul (Lot # T511019) or PBS buffer control. Two days of BID5-FC administration began when the mice started losing weight(approximately 15 days post-tumor implantation). Group 5 had 5-FCdelivered by oral gavage (OG) and all other groups IP. One more dose of5-FC was given 1 hour before sacrifice the following day. From eachbrain, the tumor was isolated and processed directly into RIPA bufferfor analysis of 5-FC and 5-FU by HPLC. A small portion of the tumor wasretained for western blot analysis.

Group Assignments and Dose Levels Group Treatment Route TX Route DosingN 1 AC3-YCD2(V) IC NONE N/A N/A 3 2 PBS IC 5FC IP 250 mg/kg 4 3 PBS IC5FC IP 500 mg/kg 2 4 AC3-YCD2(V) IC 5FC IP 250 mg/kg 3 5 AC3-YCD2(V) IC5FC OG 250 mg/kg 2 6 AC3-YCD2(V) IC 5FC IP 500 mg/kg 2 Total animals 16IC—intracranial; IP—intraperitoneal; OG—oral gavage

AC3-yCD2(V) (5 μL) was infused at 0.33 μL per minute (15 minutes,followed by a hold of 5 minutes) intracranially at the same coordinatesas TU-2449 cells were injected. 5-FC or PBS was administered IP or OGBID for 2 consecutive days and 1 hour before sacrifice.

Tissue Processing Procedures.

From each brain, tumors were isolated and trimmed if large enough formultiple analyses (more than 0.05 g). Tumors sections for HPLC analysiswere crushed in a 1.5 mL centrifuge tube using a plunger from a 1 mLsyringe. Crushed samples were mixed with 150 uL RIPA buffer and vortexedvigorously for 10 minutes. Samples were spun at 4° C. at 20000 rcf for10 minutes. Supernatants were removed and mixed thoroughly with 150 uLof 10% trichloroacetic acid and spun as above. Supernatants were removedfor analysis by the Agilent HPLC unit with a Hypersil BDS C18 column runisocratically at 1 mL/min with 95% Buffer A containing 50 mM ammoniumphosphate and 0.1% tetra-n-butylammoniumperchlorate with pH adjustmentof the buffer to 2.1 with phosphoric acid and 5% Solvent B which is 100%methanol (see WI RD-053). The run time is 5 minutes with each sample runtwice. The photodiode detector array scans from 190 to 350 nm withchromatograms selected to display at 285 nm for 5-fluorocytosine and 264nm for 5-fluorouracil. Data was expressed in relative milli absorbanceunits (mAU) of peak area from the chromatograms.

Protein Gels and Western Blots.

When sufficient tumor was available, tumor fragments for protein gelsand Western blots were mixed with a separate aliquot of RIPA lysisbuffer, and 20 ug of total protein from each sample was electrophoresedon polyacrylamide gels, Western blotted and the blot developed withsheep anti-yeast CD antibody as in Example 30. Western blot data wasscanned and quantified using BioRad Quantity One software (version4.6.7).

QPCR on Tumor Fragments.

Remaining pellets, after supernatants were removed for HPLC analysis,were extracted for genomic DNA. Samples were analyzed by qPCR forproviral integration copy number using primers and probe for MLV LTR asin example 30. Samples were also analyzed in parallel using previouslycharacterized primers and probes for the amphotropic env gene (Env2) andthe CD gene (yCD2).

yCD2 Primer and Probe set: 5′ AC3-YCD2(V) yCD2 Primer:ATCATCATGTACGGCATCCCTAG (SEQ ID NO:67) 3′ AC3-YCD2(V) yCD2 Primer:TGAACTGCTTCATCAGCTTCTTAC(SEQ ID NO:68) yCD2 Probe:/5FAM/TCATCGTCAACAACCACCACCTCGT/3BHQ_1/ (SEQ ID NO:69) These primers andprobe target and amplify the CD gene exclusively.

Env2 Primer and Probe set: Env2-Forward: (SEQ ID NO: 70)AACCTCAACCTCCCCTACAAGT Env2-Reverse: (SEQ ID NO: 71)GTTAAGCGCCTGATAGGCTC Env2-Probe: (SEQ ID NO: 72)/5TEX615/AGCCACCCCCAGGAACTGGAGATAGA/3IAbRQSp/

These primers and probe target and amplify the envelope (Env) geneexclusively.

Results. Survival Analysis.

The Kaplan Meyer survival plot is shown in FIG. 32. The median survivalof AC3-yCD2(V) control groups treated with PBS (Group 3 and 7) wasapproximately 33-38 days. The survival medians of mid and high doseAC3-yCD2(V) in combination with 5-FC (Group 6 and 4) were not reachedbefore sacrifice at 189 days. Log-Rank (Mantel-Cox) pair-wise comparisonshowed no difference in survival between the two control groups;AC3-yCD2(V) E5 dose plus PBS (Group 7) and AC3-yCD2(V) E6 dose plus PBS(Group 3).

AC3-yCD2(V) treatment at both dose levels in combination with 5-FCresulted in prolonged survival. A statistically significant survivaladvantage was observed for AC3-yCD2(V) E5 plus 5-FC (Group 6) treatedmice compared to vector plus PBS control (Group 7) mice (p<0.0354,hazard ratio 0.2605, 95% CI 0.07439 to 0.9119). A statisticallysignificant survival advantage was observed for AC3-yCD2(V) E6 plus 5-FC(Group 4) treated mice compared to vector plus PBS control (Group 3)mice (p<0.0036, hazard ratio 0.1130, 95% CI 0.02598 to 0.4911).

Short Term Experiments to Determine the Level of Viral Genome andSuper-Infection in Tu2449 Tumors In Vivo

HPLC Analysis.

In vivo conversion of 5-FC to 5-FU was detected by HPLC in all groupsdosed with Toca511 and 5-FC (FIG. 33). Group 1 that was givenAC3-yCD2(V) but no 5-FC had neither 5-FC nor 5-FU detectable signals asexpected (FIG. 33). The small counts observed (47-84) for 5-FC isattributable to background from nearby peaks on the chromatographytrace. Groups 2 and 3 that were not dosed with AC3-yCD2(V) but dosedwith varying levels of 5-FC had detectable 5-FC signals but no signalfor 5-FU. Group 4 mice dosed with AC3-yCD2(V) and 5-FC IP and Group 5mice dosed with AC3-yCD2(V) and 5-FC OG had comparable signal levels of5-FU and very low or background levels of 5-FC. Group 6 mice dosed withToca-511 and high levels of 5-FC showed readily detectable levels of5-FU and low signal for 5-FC.

CD Western Blot Analysis.

Tissue samples from isolated TU-2449 tumors were processed for westernblot analysis of CD expression. All groups (1, 4, and 5) treated withAC3-yCD2(V) had readily observable CD expression while Group 2 that wasnot given AC3-yCD2(V) did not have detectable CD expression (FIG. 34).

PCR Analysis of Genomic DNA Isolated from Tumors.

The remaining pellets, after supernatants were removed for HPLCanalysis, were extracted for genomic DNA. Samples were analyzed byquantitative PCR for proviral integration using the standardized assayand MLV-LTR primers and probe. Parallel assays using the envelope and CDgene primers and probes analyses gave similar C(t) values showing thatthe viral genome appeared quite stable. An in vitro transduced cell lineserved as positive control. The negative control was genomic tumor DNAfrom Group 2 that was not dosed with AC3-yCD2(V) and did not havedetectable signal for any of the qPCR protocols.

Summary Table of relative CD protein levels, viral vector copy #, andrelative levels of 5-FU production 5-FU (relative Relative CDCopies#/diploid peak area Group Mouse # protein levels genome units)Group 1 194 21,746 1.4 0 199 No Data 14.6 0 Group 2 191 162 0 0 187 75 00 188 −453 0 0 Group 4 185 17,349 1.8 1642 200 45,446 7.3 1576 Group 5189 25,417 3.7 942 198 23,660 6.6 1371

For samples with enough starting material for all three analyses to bedone, the relationship between integrated MLV copy number, expression ofCD, and the amount of 5-FC to 5-FU conversion is summarized in the abovetable (199 did not have material for Western analysis). The relative CDprotein levels (estimated from Western blots) vary over a three-foldrange and the DNA copy number over a 5-fold range. There is somecorrelation between DNA copy number and relative level of CD expression.All of the tumors have vector copy numbers/genome above 1, showing thateven at this early time-point after vector administration (13-14 days)superinfection of tumor cells is a usual occurrence, and may contributeto observed therapeutic effects (FIG. 32). The CD values displayedrepresent the values after average background correction, and the Group2 numbers represent the variability in that background.

This study supports the proposed mechanism of action and shows that thisefficacy can be attributed to the conversion of the 5-FC prodrug intothe anticancer drug 5-FU after delivery of the CD gene by AC3-yCD2(V).Using the TU-2449 mouse glioma model, AC3-yCD2(V) treatment incombination with 5-FC resulted in efficient in vivo conversion of 5-FCinto 5-FU. 5-FC was converted efficiently into 5-FU at two dose levels(500 and 250 mg/kg) as 5-FC levels were at least ten fold lower than thecontrols, and 5-FU levels were readily detectable in AC3-yCD2(V) treatedbut not in the untreated controls. IP or OG delivery of 5-FC did notaffect the efficiency of conversion. Tumors isolated from mice givenAC3-yCD2(V) had observable expression of CD protein that had somecorrelation with the numbers of copies of the vector genome. The numberof integrated vector genomes ranged from 1.4 to 15 copies/diploid genome(mean: 5.9). The infection here was the result of about 12 daysinfection and previous experiments with GFP vectors in other modelssuggest that this corresponds to infection of approximately 50% of thecells in the tumor, giving an adjusted vector copy number/cell of 11.8copies/diploid genome. Typical tumors are not diploid but are triploidor further polyploid with a genome larger than the diploid genome. Thiswould further increase the actual vector copy number per cell. Theexperiments described here also provide a method of testing arecombinant replication competent retrovirus for the property ofmultiple infections of a target cell population. These observationssupport the conclusion that AC3-yCD2(V) is efficiently delivering afunctional CD gene for expression in glioma cells. In the efficacy studywith this model, almost no spread of vector from the site of injection(tumor in the right cerebrum) was observed in the first 24 days. Theobservations in this study show that over the same initial period oftime there is extensive viral vector infection of the tumor, showingthat infection is quite tumor specific, and that already at this earlytime-point there is extensive super-infection of the tumor cells by theviral vector.

Example 32 Clonal Analyses of HT1080 Cell Line Infected with AC3-yCD2(V)Shows that the Majority of the Clones have Multiple Copies of the ViralVector Genome and were Susceptible to Super-Infection

The human sarcoma line HT1080 (ATCC: CCL 121) was grown in tissueculture under standard culture conditions. 2E7 cells were infected withAC3-yCD2(V) made by transient transfection on 293 cells, at amultiplicity of 0.1, allowed to grow for 14 days, and frozen down as apool. About 1 month later cells were thawed and clonal cell lines fromthis culture were isolated by limiting dilution in 96 well dishes at 0.3cells/well. The clones that grew out were expanded and analyzed by qPCRwith the MLV LTR primers for vector genome copy number per microgram DNAin triplicate. This was converted to copy number/diploid genome bydividing by 150,000, as described in example 30. The Table below liststhe clones that were analyzed and the corresponding copy number for theviral vector genome. Only 1 of 10 clones (13-5) has approximately 1 copyof the viral genome per diploid genome. The range was 0.9 to 20.4copies/cell and the mean copy number was 10.6 copies/cell. Typicaltumors are not diploid but are triploid or further polyploid with agenome larger than the diploid genome. This would further increase theactual vector copy number per cell. It is well known that normally aviral infection of this nature leads to a single or few copies of viralgenome/cell, due to resistance to superinfection through receptormasking or down regulation (see, for example, Ch3 p104 of “Retroviruses”J M Coffin, S H Hughes & H E Varmus, 1997 Cold Spring Harbor LaboratoryPress, Cold Spring Harbor N.Y.).

Listing of viral vector copy number in infected HT1080 clones infectedwith AC3-yCD2 and expanded.

Average copy Sample # Test article number/genome 1 Negative control(HT1080) 0 2 Positive control (recently 1.89 transduced HT1080 pool) 3Clone # 3-5 18.26 4 Clone# 4-1 5.28 5 Clone# 7-1 18.87 6 Clone# 8-314.04 7 Clone# 9-1 15.29 8 Clone# 10-1 9.73 9 Clone# 11-1 20.44 10Clone# 12-6 6.08 11 Clone# 13-5 0.93 12 Clone# 19-2 5.24

Therefore this is an unexpected and surprising result that confirms thein vivo tumor model data of Examples 30 and 31. More particularly, thedata demonstrate that this virus allows multiple super-infections in thegreat majority of the cells it infects, unlike normal MLV infection. Theexperiments described here also provide a method of testing arecombinant replication competent retrovirus for the property ofmultiple infections of a target cell population.

Example 33: miRNA Knockdown Experiments

Plasmid Construction.

Single or four tandem repeats of 142-3pT completely complementary to thesequence of miR 142-3p were synthesized with an endonuclease restrictionsite Not I at both ends and cloned into the corresponding Not I sitedownstream of the IRES-GFP cassette in the RCR vector (FIG. 11C-D). Thesequence of the single 142-3pT: gcggccgcGTCGACTCCATAAAGTAGGAAACACTACAgcggccgc (SEQ ID NO:35) and the sequence of four tandem repeats of142-3pT henceforth 142-3pT4X:gcggccgcGTCGACTCCATAAAGTAGGAAACACTACACGATTCCATAAAGTAGGAAACACTACAaccggtTCCATAAAGTAGGAAACACTACATCACTCCATAAAGTAGGAAACACTACAgcggccgc (SEQ IDNO:36) were synthesized by BioBasic Inc. The underlined sequences aresequence complementary to miR-142-3p in both mouse and human. Thesequence of the synthesized DNA fragments were confirmed before andafter cloning into the pAC3-emd vector using the primers:5′-CTGATCTTACTCTTTGGACCTTG-3′ (SEQ ID NO:62), and5′-CCCCTTTTTCTGGAGACTAAATAA-3′ (SEQ ID NO:63).

Cell Culture.

Human astrocytoma cells U-87MG, human prostate adenocarcinoma cells PC3,human lymphoblastic leukemia cells Sup-T1, human histocytic lymphomacells U-937 and mouse T lymphoblastic cells were obtained from ATCC.293T, U-87MG, PC3 and EL-4 cells were cultured in complete DMEM mediumcontaining 10% FBS (Hyclone), sodium pyruvate, glutamax, andpenicillin/streptomycin (Cellgro). Sup-T1 and U-937 cells were culturedin complete RPMI medium containing 10% FBS, glutamx andpenicillin/streptomycin.

Virus Production.

Virus stock was produced by transient transfection of 293T cells usingcalcium phosphate precipitation method. Cells were seeded at 2e6 cellsper 10 cm petri dish the day before transfection. Cells were transfectedwith 20 pg of pAC3-emd, pAC3-emd-142-3pT or pAC3-emd-142-3pT4X the nextday. Eighteen hours post transfection, cells were washed with PBS twiceand incubated with fresh complete culture medium. Viral supernatant wascollected approximately 42 hours post transfection and filtered througha 0.45 μm. Viral supernatant were stored in aliquots at −80° C.

Viral infection was performed by adding viral stock at 1:50 dilution in1 mL total volume in each well. AZT at 40 μm was added to preventfurther viral replication and cells were harvested 48 h post infectionfor gDNA isolation. Viral titer was determined by quantitative real timePCR (qPCR) using the following primer set and probe which will bind toall proviral DNA derived from the vectors as well as proviral DNAcontaining deleted IRES-GFP cassette: 5′-AGCCCACAACCCCTCACTC-3′ (SEQ IDNO:64), 5′-TCTCCCGAT CCCGGACGA-3′ (SEQ ID NO:65), and 5′-FAM-CCC CAA ATGAAA GAC CCC CGC TGA CG-BHQ-3′ (SEQ ID NO:66). The reaction was performedin a total volume of 20 μL containing 2× iQ SuperMix (BioRad); 0.3 μM ofeach primer and 0.1 μM of the probe. PCR reaction was performed intriplicates using CFX-96 (BioRad) thermo cycler with the followingparameters: 95° C. 10 min; and 40 cycles of 95° C. 15 s; 60° C. 1 min.Viral titer reported in transduction unit per milliliter (TU/mL) wasdetermined by calculation of Ct values derived from a standard curveranging from 1e7 copies to 10 copies of plasmid DNA and from knownamount of gDNA input, number of cells, and dilution factor of viralstock per reaction used in each reaction.

Viral Replication Kinetics.

To monitor viral replication in infected cells, 2e5 U-87MG cells, or 1e6EL4, Sup-T1, and U-937 cells were infected with pAC3-emd,pAC3-emd-142-3pT, or pAC3-emd-142-3p4X at an MOI of 0.1 (U-87MG cells)or an MOI of 2 (EL4, Sup-T1, and U-937 cells). Every 3-4 days, a portionof cells were passaged for continuing monitoring of viral replication,and a portion of cells were harvested for GFP expression by flowcytometric analysis. Cells harvested for flow cytometric analysis werewashed with PBS and centrifuged at 1000 rpm for 5 minutes. Cell pelletswere resuspended in PBS containing 1% PFA. Percentage of GFP % cellswere measured by Becton Dickison Canton II using FL1 channel. Viralreplication kinetics were obtained by plotting % GFP positive cells overtime.

Vector Stability Assay and Amplification of IRES-GFP Cassette.

U-87MG cells at 5e4 cells per well in 6-well plate were infected withtock virus at an MOI of 0.1. At d4 post infection viral supernatant from˜70% infected cells were collected and filtered through a 0.45 μm filterunit. A 1:10 dilution of the viral supernatant was then used to infectedfresh U-87MG cells seeded the night before. Four-day infected U-87 cellswere harvested for gDNA isolation for IRES-GFP PCR. This virus infectioncycle was repeated at least 12 times.

gDNA extraction was carried out using the Maxwell 16 DNA purificationkit (Promega). DNA concentration and quality was determined byspectrophotometer using Nanodrop 1000 (Thermo Scientific). To assess theintegrity of the IRES-GFP cassette in proviral DNA, standard PCR wasperformed using the following primer set: 5′-CTGATCTTACTCTTTGGACCTTG-3′(SEQ ID NO:62), and 5′-CCCC TTTTT CTGGAGACTAAATAA-3′ (SEQ ID NO:63). Thereaction was performed in total volume of 25 μL containing 0.4 μM ofeach primer, 0.4 mM dNTP and 2.5 unit of SuperTaq (Ambion), and the PCRreaction was performed with the following parameters: 95° C. 10 min; and40 cycles of 95° C. 15 s; 60° C. 1 min. 95° C. 2 min and 40 cycles of95° C., 15 s; 55° C., 30 s; 72° C., 1 min, followed by 72° C., 5 min.One fifth of the PCR reaction was loaded on 1% agarose gel to resolvePCR products. The expected PCR product of an intact IRES-GFP cassette is˜1.2 kb. PCR products less than 1.2 kb indicates partial or completedeletion in the IRES-GFP region.

For experiment in which the PCR products were excised from the gel forsequencing, gel extraction kit (Qiagen) was used to obtained PCRproduct. The same set of primers used for PCR reaction was used for PCRproduct sequencing.

miRNA Expression Assay.

miRNA-enriched RNA was extracted from U-87MG, 293T, Sup-T1, U-937 andSup-T1 cells by using the mirVana miRNA isolation kit followed by DNasetreatment (Ambion) according to manufacturer's protocols. TaqmanmicroRNA reverse transcription kit was used with RT primer formiR-142-3p (assay ID #000464) and RNU6 (assay ID #001093) and sno135(assay #001230) as endogenous controls for human and mouse cell lines,respectively, to produce cDNA for TaqMan microRNA assay (assay ID #TM000464), (Ambion). Reverse transcription and quantitative PCRreactions were set up and carried out according to manufacturer'sprotocols. 2^(−ΔCt) was calculated to obtain miR-142-3p expressionrelative to endogenous control.

Having confirmed the expression of miR142-3p in hematopoietic-lineagederived cells, cells were then infected with pAC3-emd, pAC3-emd-142-3pTand pAC3-emd-142-3pT4X vectors, respectively, at MOI 2. The data showedthat in EL4 cells viral replication of parental vector pAC3-emd wasextremely slow in early time with a lag phase that lasted up to 30 daysand reached to maximal infectivity (˜70% infectivity) by day 80 postinfection. In contrast, GFP expression and viral replication ofpAC3-emd-142-3pT and pAC3-emd-142-3pT4X vectors were completelyabrogated in early time during infection (FIG. 11D).

A number of embodiments of the disclosure have been described.Nevertheless, it will be understood that various modifications may bemade without departing from the spirit and scope of the disclosure.Accordingly, other embodiments are within the scope of the followingclaims.

1-60. (canceled)
 61. A recombinant replication competent retroviruscomprising: a retroviral GAG protein; a retroviral POL protein; aretroviral envelope; a retroviral RNA polynucleotide comprising 3′untranslated region (U3) and repeat region (R) sequences at the 3′ endof the retroviral polynucleotide sequence, an R and 5′ untranslatedregion (U5) sequence at the 5′ end of the retroviral polynucleotide, agag nucleic acid domain, a pol nucleic acid domain and an env nucleicacid domain located between the U5 and U3 regions; a cassette comprisingan internal ribosome entry site (IRES) upstream and operably linked to aheterologous polynucleotide comprising a binding domain, wherein thecassette is positioned 5′ to the U3 region and 3′ to the env nucleicacid domain; and cis-acting sequences necessary for reversetranscription, packaging and integration in a target cell.
 62. Theretrovirus of claim 61, wherein the retroviral polynucleotide sequenceis recombinantly engineered from a virus selected from the groupconsisting of murine leukemia virus (MLV), Moloney murine leukemia virus(MoMLV), Feline leukemia virus (FeLV), Baboon endogenous retrovirus(BEV), porcine endogenous virus (PERV), the cat derived retrovirusRD114, squirrel monkey retrovirus, Xenotropic murine leukemiavirus-related virus (XMRV), avian reticuloendotheliosis virus (REV), orGibbon ape leukemia virus (GALV).
 63. The retrovirus of claim 61,wherein the retroviral envelope is an amphotropic MLV envelope.
 64. Theretrovirus of claim 61, wherein the retrovirus is a gammaretrovirus. 65.The retrovirus of claim 61, wherein the binding domain comprises anantibody or antibody fragment.
 66. The retrovirus of claim 61, whereinthe retrovirus infects cancer cells of a cancer.
 67. The retrovirus ofclaim 66, wherein the cancer cell is selected from the group consistingof lung cancer, colon-rectum cancer, breast cancer, prostate cancer,urinary tract cancer, uterine cancer, brain cancer, head and neckcancer, pancreatic cancer, melanoma, stomach cancer and ovarian cancer.68. The retrovirus of claim 61, further comprising a promoter cassettecomprising a pol III promoter that is positioned 5′ to the U3 region and3′ to the env nucleic acid domain.
 69. The retrovirus of claim 68,wherein the pol III promoter is an H1 or U6 promoter.
 70. The retrovirusof claim 61, wherein the 3′ U3-R domain is derived from agammaretrovirus.
 71. The retrovirus according to claim 68, wherein thepromoter cassette comprises the pol III promoter operably linked to aheterologous nucleic acid sequence comprising an inhibitorypolynucleotide.
 72. The retrovirus according to claim 71, wherein theinhibitory polynucleotide comprises an miRNA, RNAi or siRNA sequence.73. A recombinant retroviral polynucleotide genome for producing aretrovirus of claim
 61. 74. A method of treating a cell proliferativedisorder comprising administering a retrovirus of claim 61 to a subjecthaving a cell proliferative disorder under conditions such that theretrovirus infects cells with the disorder and contacting the subjectwith an anti-cancer agent or chemotherapeutic agent.
 75. The method ofclaim 74, wherein the anti-cancer agent is selected from the groupconsisting of bevacizumab, pegaptanib, ranibizumab, sorafenib,sunitinib, AE-941, VEGF Trap, pazopanib, vandetanib, vatalanib,cediranib, fenretinide, squalamine, INGN-241, oral tetrathiomolybdate,tetrathiomolybdate, Panzem NCD, 2-methoxyestradiol, AEE-788, AG-013958,bevasiranib sodium, AMG-706, axitinib, BIBF-1120, CDP-791, CP-547632,PI-88, SU-14813, SU-6668, XL-647, XL-999, IMC-1121B, ABT-869,BAY-57-9352, BAY-73-4506, BMS-582664, CEP-7055, CHIR-265, CT-322,CX-3542, E-7080, ENMD-1198, OSI-930, PTC-299, Sirna-027, TKI-258,Veglin, XL-184, or ZK-304709.
 76. The method of claim 74, wherein theretrovirus is administered from about 10³ to 10⁷ TU/g brain weight. 77.The method of claim 76, wherein the retrovirus is administered fromabout 10⁴ to 10⁶ TU/g brain weight.
 78. The method of claim 77, whereinthe retrovirus is administered from about 10⁵ to 10¹¹ TU/g brain weight.